This is going to be personal preference.
We love BBB, I will say I would buy cotton dresses if your worried about it being uncomfortable at the party. The dresses they sell are amazing but my kids never last long in them and find them uncomfortable especially if it’s hot. But some kids wear them all day, my kids won’t.
Is it a good use of party time, probably not, wait times are low all day, but since the party tech doesn’t start till 7, losing 330-430 for this isn’t horrible.
How old are your kids? Will you have the opportunity to do this again? My girls are 4/8 and I don’t think the 8 year old will want to do it again and the 4 year old probably won’t do it if the 8 year old isn’t, so I would do it. But it is very situational.