Am going to be doing a job involving approximately ten 3-5 year olds.  Having never worked with children before, I am unsure as to what type of make up is required - eg do I need to use foundation or would a light powder be enough.  And should I use lip balm or is that unnecessary.

And in terms of hair - any tips would be appreciated eg how to get them to sit still long enough...

thanks

I wouldn't bother with foundation for children, they will usually end up looking too made-up.  I would do a light powdering for shine, brush the eyebrows, maybe a bit of clear mascara on the brows to hold them in place.  Lip balm just for dry lips.  Little kids always have great skin until those pesky hormones kick in, so keep it light and simple.

I do spot foundation as needed, because kids almost always have a scrap or a bruise for all that play time. Other than that I do some powder over a light coat of primer. A bit of blush on the cheeks. Cream blush works really nice for kids because it can look so natural. Some rosebud salve on the lips and brushing those eye brows if needed.

I've compared doing makeup on toddlers to attempting to put makeup on a rabid cat. It's an adventure and sometimes you get hurt. It's a lot of fun working with kids. Some of them really love the makeup, but some of them get really angry about it.

Some of them have NO problem sitting for makeup, especially if they've done any pageants or performing in the past. I had a six year old point at my table one time and dictate to me what her colors were. I wasn't sure if it was cute or creepy, but it's a memory that will always stick with me
I pretty much do what Chelsea said...
As far as complexion goes, I usually stop after a light dusting of powder, so I don't irritate their skin. Kids skin can be super-sensitive and it is usually perfect anyway. Skip all the heavy products and avoid the possibility of allergic reactions. Their brows can be crazy, so lay them down. I've added blush if it was asked of me, but I always do lip balm, and sometimes with a little hint of sheer color to make lips pop if that's what the people want.

Rosebud Salve... awesome! I'm using that next time.

(This is a good topic and will probably come up again... how can we add it to FAQs?)

Thank you for everyone's advice!  Much appreciated

It really all depends on what the project is.
I started dance & performing when I was 3, so I had to have the whole sha-bang.
You could do anything from tinted lipgloss & some mascara, to full eyes, foundation/ powder, lipstic of whatever color, & blush.
Just depends what it's for.

I did a commercial for a children's network where we had to make up about thirty 4-10 year olds. It wasn't as bad as I thought it would be and the kids all sat in the chair without getting too antsy. If you ask them questions they get distracted (they're only in the chair for a short amount of time anyway.)

As far as makeup, check for any food or crust that might be leftover from the last meal that needs to be wiped clean. Then just a little powder, maybe some neutralizing under the eyes and spot reduction for scratches/bruises.

With kids, especially the young ones, less is more. In the end, they still need to look like kids.

Those are pretty young kids.

This is pretty much what I do with them:

Baby wipe face (usually there is food/dry skin/toothpaste) + check for eye crusties
Moisturize, then ask parents if they are ok with sunscreen (if you're shooting outside)
Clean crusty snotty nose (this is an on-going thing)
Cover scratches or bruises
Clean hands + nails
Lip balm
If they can sit still enough, correct the dark circles (a lot of kids surprisingly have them)

I don't bother with powder, unless they have very uneven skintone.

As far as hair goes, sometimes I'll have the mom help me if they are fidgety.

ALWAYS check their mouth and hands during the course of the day (Cheetos + Doritos are my nemesi), as they snack often. If you see any type of food or candy on the craft service table that would possibly stain the mouth or tongue, politely ask the parents if the kids could refrain eating them until after the shoot is over.

I'm also a MUA and a mom.

I think foundation looks tacky on kids, besides they have a naturally good texture and usually even tone. I have just done a small bit of powder, a light colored gloss on the girls lips and clear aquaphor on the boys lips. I use clear mascara on lashes and brows. maybe the tiniest tad bit of light blush. That's it.

As far as getting them to sit still, nothing works better than cartoons (a close second is games on the iphone, or laptop).

Spot concealer and/or color correct under eyes (kids have thin skin and the veins are close to the surface giving the under eye a blue tinge) and anywhere else necessary.  Lip balm or gloss if needed. A hint if light blush if necessary, and if not, a little swipe with the empty blush brush anyway to make them feel special.  Hair:  make sure you have a spray bottle of water for static, hair spray, and elastics, headbands, etc.  Learn to gently comb knotty hair cause it will be knotty.  Be careful with your hot tools as kids can be fidgety.

Thank you again guys for all your advice

It is for a TVC - should have mentioned that but you all gave me the answers I pretty much needed. 

I wouldn't even do much at ALL. Maybe lip balm, and I MIGHT put some highlighter in the inner corners of their eyes to brighten their eyes a bit. But no foundation or any other stuff like that.

I'd focus on hair and that's it, personally.

Wow! First of all good luck to you

hmm... i would do a light powder just to get rid of shine if it's for photos, if it is for an event, then i would leave the powder out altogether. Brush the brows into a nice shape. Cream blush can look very natural if applied with a light hand and is great for children makeup, adding to their already youthful glow. And last, add a tinted lipbalm, as a lipstick would definetly be too much. Or lipgloss could be okay depending on the type and the color. Hope this helps!

EDIT: For hair, childrens hair usually is fine like baby hair, so to keep fly-away's down, spritz some Graftobian setting spray. it works! and it's not as thick and sticky as a hairspray.

I'd recommend using balm on the lips but avoiding anything glossy/sticky as it can lead to them pressing their lips together or chewing on the lips when they should be smiling!