Big nervous. Need advice

Ok so tomorrow my boyfriend daughter is suppose to be coming over while he works. Me and my boyfriend have an almost 2 year old son together and his daughter loves her little brother. She always wants to hold him or play with him. My son only met his sister a handful of times but this will be my first time babysitting her and I have no idea what to do as far as "fun" im afraid she won't like me or that I might bore her. My boyfriend said to paint her nails watch a movie with her and to think of some more things but idk what else to do. Need advice. I only have a son and have boy toys over here. I just need help lol. Before anyone asks, me and my boyfriend been together almost 3 years and the reason she only met her brother a few times is because when i had my son adults didnt want to act like adults. I will easily welcome his daughter with open arms because she's my son sister. But unfortunately her mom is a different type of person. I just want her and him to grow up together and for all of us to be a family.