I don't usually recommend Ramon's because I think they are too pricey for the rooms but the location, grounds and dock are hard to beat, so probably just what you guys want for *this* trip. Make sure that you don't get put in the garden rooms in the back of the property. If you do, you almost might as well have been at Steve and Becky's.
Banana's is a pretty nice place but I don't think it's got what you guys are after on this trip and it's a jaunt to the south.
Book Ramon's and don't look back. While you are there, if you have the time, take a golf cart and do a tour of some of the other resorts in anticipation of your next trip down. So make a list of the places you'd like to see, Coconuts, Banana's, Banyan Bay, Caribe Island, Mata's, Paradise Villas, Belize Yacht Club, etc., etc. Have a drink at each place, make notes on your list in case you have too many drinks.
Oh, and while you are at Ramon's you can easily take a look at the Palms and Belizean Reef for your next trip too. Those hotels give you the same locale, as well as easy access to the beach and dock at Ramon's.
You shouldn't need to book your diving *before* you go, but when you arrive, go to Ramon's dive shop and see if they use Amigo's for the Blue Hole trip. Get the lay of the land, as it were, as to what you need to do to get set up for diving with them. If they do use Amigos for the Blue Hole trip, you might be better off just to use Ramon's dive shop. Though I still like Amigo's better, you guys are going to be right at Ramon's and aren't diving every day. That slight convenience might offset the difference between the two operations.
The boats return to the home dock between dives on the two tank dives and so sometimes it is nice to be able to run up to your room and get something you forgot or do some business. You'd be able to do that from Ramon's dive op but if you were diving Amigo's, then you'd be hanging at their dock instead and doing your business at Cholo's. Amigo's will still drop you off at your dock after your diving is done for the day. You don't have to walk down to the shop in the morning or back after diving.
Do book your Blue Hole trip the evening you arrive. Amigo's boat doesn't go to the Blue Hole every day and the trips can fill up fast as the trip approaches.