I'm totally game (especially because there is a cosplay I've wanted to throw together for ages that actually requires roller skates)!
I vote for some day in between the eighth and twentieth. Chose those two arbitrarily.
If it's late July I hope it's in the afternoon, because by then I'm already back at school.
...ah, I just thought of something! If the group was large enough (unlikely, but one can hope), do you think we could influence their musical decisions? I dislike skate park music, some kind of option would be nice.