I book rooms for my parents a couple of times a year. They always get lounge access (when there is a lounge) and room upgrades and a welcome note and treat. I assume it is individual hotel management decision to do so as they aren't entitled to the perks.

I would get your parents on the reservation in writing and either do a credit card authorization for them or make sure they are prepared to give a credit card at check in. The one time my parents had trouble checking in was when the agent at the front desk insisted they could not check in (their name was on the reservation) because the credit card on file was in my name. It was cleared up by the hotel manager.