from what I have read, they encourage you to place the kids in the correct group to see how that goes before moving them around. I think they usually find that it works out fine. If you find that it is not, you can talk to the CMs and ask for one of them to be moved, I think they usually move the older one down. Just know that once you make a move, they usually request that you stick to it as they don't want kids moving in and out of age groups for safety reasons. Make sure you let the CMs know of your concerns in the beginning and they will do what they can to make them comfortable in their groups. So I guess the answer is yes, but wait and see before moving them around. HTH