A place to host a brunch style bridal shower in Nassau County, NY

Does anyone know of any good places to host a brunch style bridal shower at a reasonable price?

Not sure what reasonable means to you, but you can literally call any restaurant and ask if they have a private room where you can host a bridal shower.  Here are a few I've been to/know of them having a private room:

Villa D'Aqua (I had my bridal shower there)
Luigi's Restaurant & Bar
Maggiano's
Novita
Waterzooi

For more, I'd suggest using Yelp and in the search field type "private room restaurants".  You can do the same on Google.  Best of luck.