Ya, a queen won't lay any more than what bees there is to cover the brood. By all means, give them a frame of the oldest capped brood that you can find. I know it sounds overbearing, but don't forget to give em a couple shakes of bees also.
From the sounds of it, they could be put in a nuc box, if you have one, for a couple three weeks to build up their population. My ole bk'n bud poo poos it, but I think if a hive is in too big of a box they lose confidence and get in a circle the wagons mode and don't grow easily.