I have some kids around here kind of like that. They live in a tough situation. Mom works hard, and step-dad drinks too much, and always quits his job when Mom takes a vacation! Last summer I started inviting the kids over to play with ponies. They love it! Mom comes over too...we buy Girlscout cookies from the girls, and have given the 12 year old girl some one on one time to help get her out of the house. I plan on introducing the 12 year old to horse shows this summer.
I think calling child protection services might be a bid idea. It sounds like Dad has enough on his plate. Get to know the kids first, then decide what the next step must be.
Kim R