You can buy a 10 X 20 tent in various colors, (too bad the pink is out of stock), for a little more than $90. We bought the 10 X 30 last year. It really is nice quality, and my husband put it up by himself, although the directions say it takes about six people to do so. Here is the link:
Good luck with the Princess Party! The pink tent would be just perfect, but the white one will do for that and any other event. Also be sure to give your in-laws an estimate on how much they'll have to pay for their anniversary party. Just think how much money they'll save by using their dusty old tent, LOL!