A couple of options that should be possible if you're willing to do a little coordinating. If you have all day on Roatan - like 8-4 or so, here's a couple of options. fwiw, we spent a week in Roatan and always look for the best non-cattle diving.
First of all, AKR is near Spooky Channel, which we agreed was probably the best dive we did all week on the North side (West End). A close second was Texas. So if you could find someone near the West End to take you there that would be a good combo. Coconut Tree does them both but maybe not on the same trip - depends on the currents/winds at times. I would guess so does AKR as Spooky is closer to them.
Personally I'd go with Coconut Tree, they have two boats and limit divers to about 12-15, AKR has 6-8 larger boats. We did the dolphin dive at AKR, six of us and had a boat to ourselves. Just counting tank racks, I'd say the boats at AKR could hold about 25 divers. Granted they're nice boats, dual ladders and plenty of room. But there was 8 of them!
Modern fleet of three Custom Pro 48 and seven Pro 42 dive boats
Gay, the owner of CTD posts here as cocoloca, Bay Island Diver above is Will, their course director. Afterwards there's at least a dozen places to get lunch nearby in the West End as CTD is in the heart of it. Even do a little shopping, they'll hold your gear. And the cab stand is literally across the street from the diveshop. At AKR, you'd be eating at AKR, or back in Coxen Hole, AKR is pretty much by itself.
Another option would be to stay south closer to Coxen Hole. I liked the West End much better but since you're only there a day...We also did a morning of diving with
Barefoot Divers, they're the on site diveop at Barefoot Cay - probably closest to Coxen Hole. Dove both Mary's Place and the Prince Albert wreck off Cocoview one morning before lunch. They had a smaller boat so would be limited to about 10-12 or so. You'd have to check with them on availability as they're the onsite op for the resort so may have a conflict with their guests diving schedule. Nice, new diveop and boat, they were just finishing it last May.
I would guess Cocoview could do the same, they also have a cruise dive program. For all the good press Cocoview gets, one look at the size of their fleet was enough for me to look elsewhere. I didn't go on the Mary's Place dive but my buddies said it was over-rated. ymmv.
Another more involved option would be to dive both encounters - Dolphins and Sharks - while on Roatan.
We actually were able to do the dolphin dive at AKR followed by the Shark Dive and were done by 2:00 or so. If you went to AKR first, you could be back in Coxen Hole mid-afternoon easily for lunch. I don't recall the times for the dolphin dive but we were the only ones doing it that morning. I think it might've been around 9am. It's a short ride across to the key to meet the dolphins, then a 5min ride to the divesite. And a 45min. time limited dive. As I said, we did both in one morning but had to rush to the Shark Dive, couldn't even wait at AKR for the video to be ready.
Contact a diveop and have them book you on the Waihuka Shark Dive. There's also
booking agents that can help with that. I think the cruise line also books it, but it might be more $$.
I'd suggest doing it all via cabs, it can't be more than about $10pp each trip. Less if you negotiate up-front. I don't know if you could do this though as it would depend on how early you can get off the boat and to AKR, you'd need to be at Waihuka around 11 for the 2nd shark dive - I think the 2pm dive would be cutting it too close for you to get back to the ship.