I honestly don't see anything wrong with just having a room to strictly dance in. Since its your birthday Jam, people would have fun regardless of which venue/idea you decide to go with. In the end, its all up to you and how much you want to spend. That first picture looks suuuuper pricy compared to the second one to be honest. But it is your, 21st birthday? So it should be something special for sure and seems like people would enjoy a scene where they could dance AND do some other fun activities on top of that. But again, i'm sure which ever idea you decide to go with, it'll be a blast.

hope this helps!