FWIW, Boatwright's isn't open for lunch, but perhaps they can arrange a special meal through the wedding coordinator.
Depending on the time, boats to Disney Springs are not super frequent during the day time. They start to pick up around 4pm. Disney Springs is a good idea, and I'm sure some places have private rooms even. But I'd keep potential boat delays in mind when figuring out times if that's the route you take.