I could be wrong about this but I don't think you can get room service until later in the evening on your first day aboard.
There are places that you can get munchies from, Topsiders Buffet may have cheese and crackers that you can plate up yourself. Or you could get slices of pizza from Pinnochio's, there is all kinds of yummys at Pluto's and Scoop's is open till 3:30.
P.S. We've been on 5 Disney cruises and have made many plans to meet up with people on embarkment day, people don't always show up. There is alot going on. Everyone trying to get into their staterooms to unpack or going to lunch at Topsiders or Parrot Cay. the kids just want to play at the pool. Ressie to be made at the spa, Palo, shore excursions, changing dinner times and registration for the kids into the kids clubs. BTW at 2:30 there is a shore excursion talk they give away prizes and chances to win free island rental. The safety drill is at 4:00 that last about 30 minutes then just about everyone runs to watch the ship pull away if the docks. Before you know it it's time for the folks who have early seating to get ready for dinner. I'm just telling you all of this so you don't get your feelings hurt if only a few people show up. You may want to try for a another meet later on in the week, like a DIS Brunch or cocktails in one of the lounges.