+1. I always do that even if all reservations are under my name as I usually book reward nights individually per night for greater flexibility later on.

I did the same today for a stay at the IC Davos (CH). Emailed hotel all 3 reservation numbers (2 nights reservation for AMB Cert, 1 night reservation for points under my name, 2 nights reservation on points under my GFs name) and asked for allocation of one room for entire stay. Usually possible and never had trouble, but also never left it to chance.

BTW, don't expect hotels to pick up on your multiple reservations even if made by the same person / from same PC account. Many properties prepare a day or two in advance of arrival only and they totally don't catch it (yes how hard can it be to look for reservations made with the same PC#?).