For the boys, shave their heads. You may still need to nit-pick what little hair they have left, but it will pretty much solve the problem for them. Not so simple for you and your little girl.
Buy the red Rid metal comb for combing out the lice, nits and eggs. Someone on here recommended putting a mixture of white Pantene conditioner and baking soda on the hair to be combed. Rinse out the comb with hot water between each pass. The conditioner will help with the combing. The grittiness of the baking soda will help catch up the nits and eggs.
The combing needs to be done daily for 2 weeks, until you're sure everything is out. It's a major pain. We did a combination of the medicated shampoo and the combing. It was easier for my son since I could shave his head. Not so easy for me.
I recently found out very good friends have a bad case of lice (not from us, we had it 9 months ago). I bought some of the Fairy Tales rosemary spray and put it on my son's hair and my hair to ward off the lice. Hope it works because I sure don't want to go through THAT again!
Best of luck!