I've been to siddhi vinayak a numerous of times on occasion of weddings and ceremonies and its a very good place to be. The area is quite big the decoration suits the place. The catch here is that its a vegan place.
Other than that the place itself is at a hub of Siliguri town making it possible for everyone to attend the ceremony and return to their respective places in public transport if they don't have any. Its right on the station feeder road and has loads of transportation available. So in short its a very good place to hold a reception or a wedding ceremony