Your greenhouse event center sounds very much like some retail garden centers. They are in greenhouses, have nice plants all around, and cater to relatively large numbers of people looking around. Start with some tours of several of these garden centers to get an idea of what all is involved. The garden center manager should be able to give you many do's and don'ts. Even though you mention "not growing... plants" , you would be if you have an indoor garden look. Yours would have many fewer plants and more open area for tables and chairs, but the climate controls, etc. would be similar to a retail garden center, I suspect.

A couple of places I know of that grow plants also host weddings and events. They have areas that can be easily arranged to accomodate different activities, and probably use the plants they are selling as the decorations. If you do not plan to sell plants, you will still be needing to grow or buy some, so there might be some motivation to have a sales business also.
Renais