...or I have any for any other reason, they are smaller than usual until about 6 weeks old. From then on they seem to be the same size, not stunted at all. I wouldn't want to go through the hassles of the potential cannibalism, etc., of their first litters, though, but even if this happens, the colony will likely stablilize eventually.
Your adult pair might kill them immediately, so I would introduce them one morning after cleaning the cage, and watch them closely all day. If they don't kill them pretty quickly, leave them in, hopefully through the birth and rearing of a litter by the adults, and if they are well fed for the next few weeks, they will likley make good breeders themselves.