Should be fine for a month, the more small cichlids in there the better to spread the aggression around, and they will feel safer in a group. Get a bunch of flowerpots and hiding spots, the more the better.
Change of plans anyway - looks like I managed to find homes for my goldfish pretty much instantly (around here, I'm always prepared to have to hold on to fish for a bit after looking to rehome them, finding homes for large fish can be like pulling teeth). So by the time the pearsei and argentea get here, the 135gal should be cleared of goldfish and ready for the new arrivals, and I can avoid having to put them in the 40