Could me and my sister be in a TWEEN fitness class?

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My sister is 7 and I'm 12. I'm not really sure what a tween is, but I think it's like a teen and a preteen or something? Yeah, idk. It's over the summer, for one hour a week. I don't need to lose the weight, I just like to be healthy and have always been that way. On the other hand my sister is 4 ft and about 69 pounds. She's not fat, but she could lose a bit of weight to be more healthy. What do you think? In the fitness class, there is trampolines, group sports, exercises, yoga, pilates, etc. It's like a Tuesday night from 530 to 630, something like that. Is it okay for both of us?