Good question. I too would like to gift a stay for my in-laws as well but didn't know I could reserve it under their name but into my account. I wondered too if they would benefit from my Gold membership like comp breakfast and etc.
By the way, I'm fairly new to the system and glad I can get answers and tips on here. Thanks!
j & Thor,
Technically the answer is no. The platinum member is supposed to be present in order to receive the benefits. However I have made reservations for family members in the past with their name under my account and they were able to receive platinum perks without me being present. Most likely it depends on the individual property and whether or not they decide to enforce the policy.