Hi Amy M.
Do you have outdoor space? If so, I would take them both for a "race" or "crazy dance party" around the space for 15-30 minutes ASAP after lunch, so that they're ready to calm their bodies and find a center. I find that once kids are fueled with food, they're ready to burn it off, and won't settle down until they have an opportunity to do so.
After that, you could try giving everyone their own peaceful space.
Would your 5 year-old be...