I think your on the right track. Since you already have sealed queen cells, I would probably let them finish raising their queen with an eye toward requeening in the fall. I don't see alot of time savings ordering a new one now, and strong colonies frequently raise strong queens.
You mention the new colony being very strong. Realize you are going to have a pretty large gap in brood rearing in the strong colony very soon. Your package bees are probably about to make some huge growth on their own. In a few weeks, with both colonies queenright and things having settled down, I think you could make a better decision about giving a frame of brood or 2, to the weak colony. They may not be that weak by then, while the strong colony may be suffering some.