Babysitting activities?!?

Ok I'm 15 and I'm gonna be babysitting a 6, 9, and 13 year old (boy, girl, boy respectively) next week for four days and I need some activities that will keep them busy and not bored. I'll be at their house which is good so they won't feel awkward plus the house is huge and they have a pool and two dogs who I'll also have to watch (but I'm fine with that since I've got 7 pets of my own)....I was thinking of baking brownies, swimming, watching movies, doing the girl's makeup but that's all I got. Help please?! Thanx so much