I cannot believe Disney World would force you to eat at a restaurant to experience your husband diving. You'll have just as much fun as your husband. I did this for my dad and stepmother a few years ago and the families can be a part of the dive. They will videotape you "greeting" your diver(s) in the tank.
I wouldn't worry about it right now. Your husband will have to check in at Guest Relations and there will be a couple of Cast Members there to collect the C cards and make sure everyone is there. They do a great job of meeting everyone. At that time, tell the CM that you want to watch the dive. They will tell you how to do that. When we went, the CMs at the slow moving cars (they were open then) gladly opened up a back door for us to get up to the tanks. I'm sure the Coral Reef people will be fine. Trust me, the entire restaurant will love being a part of this. My dad said he was hard pressed to continue on during this portion of the dive because the kids in the restaurant were going crazy at seeing the divers.
Just talk to the CMs at the check in and you'll be OK.
And for what it's worth - make a good meeing up point for after the dive. It'll take him a while to go through the shower and changing. They will also be able to see the video taken. Make plans to buy that thing. It's fantastic. About $40 but well worth it. Plan to meet somewhere about an hour after he ascends. I suggest the outside seating area at the Fountain View bakery.
Also, remember that the entire fee is tax deductible since everything goes to research.
He's going to have a blast! And so will you.