Be sure that the reservation is in your wife's name. If in yours, you will only get the benefits due a "lowly Silver."

The only benefit that you will definitely get as a Gold is Concierge Lounge access, regardless of room assignment.

Room upgrades are on an "as available" basis and you will be behind all of the Platinums and competing with the other Golds. It wouldn't hurt to call Marriott Reservations so they can annotate your reservation with any special requests as well as a request for an upgrade.