I have the same problem with my daughters hair. We’ve had really good luck with pantene (shampoo, conditioner & detangler – about $4.00 each) and with Breck detangler for kids which I found at Deal$ for $1.00. Someone posted on one of the groups I belong to awhile back that satin pillowcases help prevent tangles while sleeping.
I haven’t tried that yet though.
Good luck! Jessica – mom to 2 1/2 year old b/g twins Teddy & Delcie & 1 on the way