Hi @Corine123
In my experience, it is highly unlikely for you to find someone to host a party for 50 people no matter how tame the party as an airbnb. Also, I believe there is a company policy against booking airbnb properties for parties.
Perhaps you would be better off with a venue instead of an airbnb property? Bigger hotels in my area begun to offer their smaller meeting rooms, such as the business center or the conference room, or a couple of suites as baby shower venues and they really do a good job of it.
The wedding destination type places (there are a bunch of castle like looking wedding venues in NJ, I'm sure MA has them) also began to offer smaller meeting rooms for such occasions complete with living room furniture etc. Anyway, I think you might have better luck with a place specifically designed to host 50 people comfortably.