I am in the same situation as you and generally need to fit 4 people in a room. What I have found among the big chains is that Marriott seems to be the best - in getting a room with 2 double beds (as in most US hotels). This does not seem to extend to the Renaissance Hotels. Also note that not all Marriotts will let you put 4 in a room.

The downside is that if you are paying for this stay then it can be quite expensive. It does work well if you are redeeming points.