Shooting families with small kids automatically reduces the number of keepers ... generally, because it means I intentionally shoot more total pictures!
Last two shoots I did I gave them my rate posted proofs on my site let them pick 10 for me to edit and give them on CD. I gave them a few more than what they picked some I liked.
Say you have a family of 4 and you shoot the together 20 shots maybe 2 or 3 are great so they pick. Other wise they would want me to edit every photo.
L2
I normally have clients bring the kids' favorite toys and have my assistant twirl them around behind me to try to get the kids' attention. I have had a pretty decent amount of success with that. Of course, it's always better if the parents aren't in the shot and they can get the kids' attention for me.