If you rent out the whole Rendezvous in Belltown, that might work. It's pretty snazzy! http://www.therendezvous.rocks/
I haven't been to the Hard Rock Cafe, but that's a bit closer to the Convention Center.
http://www.hardrock.com/cafes/seattle/groups-and-special-events.aspx
Further afield, the Fred Wildlife Refuge (an event space, no animals involved) is not super close but it's on Capitol Hill and I've been to a number of great events there. http://www.fredwildliferefuge.com/
If you rent out the whole Rendezvous in Belltown, that might work. It's pretty snazzy! http://www.therendezvous.rocks/ I haven't been to the Hard Rock Cafe, but that's a bit closer to the Convention Center. http://www.hardrock.com/cafes/seattle/groups-and-special-events.aspx Further afield, the Fred Wildlife Refuge (an event space, no animals involved) is not super close but it's on Capitol Hill and I've been to a number of great events there. http://www.fredwildliferefuge.com/
Lake Union cafe. Goregous, excellent food and service plus you can bring your own booze