Fun things to do with my mom?

My sister is going to be in camp all week. My mom said that she wanted to have a mommy/daughter week! I'm excited because we never do anything like this. I was thinking we could go to the spa and get manicures, facials, massages, etc. But that could get really expensive and we are on a budget. I have a lot of expensive new clothes already so I don't think that shopping would be a good option. Any ideas? I am 11 by the way. Oh and please put things that would be fun for my mom too.