"is the Fremont lodging doable without a car?"

Yes - you can do fine w/o a car. The BART is terrific, plus there will be several H-Ters with cars who could ferry folks around if needed. I think you said you were arriving on Thurs. If so, You might want to think about staying Thurs and Friday in SF and Sat/Sun in Fremont. That way you could do a lot of SF sightseeing on foot/cablecar/streetcar and then you could join the party in Fremont for a night or two.