AAAAHHHHHH!!!!!!!! Little kids everywhere. what to do next time?

I babysit on a regular basis for a couple who has 3 kids. A 5 yo who listens when he wants to, a 3 yo who has some sort of very mild autism, and a 2 yo who has her moments. She's very stubborn. When she's happy she's a bundle of joy, when she's not, look out for screaming bloody murder (like when mommy just walked out the door). Anyhoo, i was watching them with my friend once (I'm almost 15, friend is 15. i didn't feel comfortable watching them by myself since it was all day), and we were playing with a sheet (of all things) and one of them would get in the middle, we'd pick up the sides and swing them back and forth. Now every stinkin' time I watch them, it's "swing, swing, swing" and since it's just me, I can't do it (since you need 2 older people), and the younger 2 scream. I also have another problem when I got them dressed up in swimsuits one time, and we laid down towels and played with water in the kitchen floor. now every time it's "water, water".