That should be fine and is normally a good idea. But the broader point is why do you thing you have a strong queen if they aren't building up? Maybe she was poorly mated. Is there a good capped brood pattern or just good egg pattern? If they've had a good shot this season (like this isn't a young split) but they're languishing nonetheless, I'd just combine them with the big hive for overwintering and re-split in spring.
I'd say figure out why they aren't building up before you put a lot of effort into the colony; if there's an underlying problem just adding more bees is unlikely to fix it.
Bees, brews and fun
in Lyons, CO