I've stayed at the Westin Aruba. really nice place.
first thing. See if you can still do the room upgrade (to a suite) for an extra $99 or $100. We did it because it included a $100 food/drink credit,, which you'll easily spend regardless. So worth it.
2nd thing. Eat at Pago Pago (if it's still there). Great steaks and great lobster bisque.
When we stayed there it was still the Wyndham. It changed in the last few years. The food there wasn't cheap, but it isn't anywhere on the island. but the facility was nice. The pool was nice and we really liked it. The hot tub was kinda nasty though.
if you want a "straw umbrella hut" get down there early and get your name on the list each morning. They run out quickly and the sun in Aruba is intense. If it's windy (which it is most days) then get one closer to the hotel and farther from the water. It'll reduce the 'sand blasting'.
The only real negative when we were there was that the hotel bar SUCKED. The drinks were really poor quality and you had to wait 10 minutes at the bar to get a bartender to make a drink because they were understaffed. When you pay $7-8 bucks for a drink, you expect it to be at least decent. we were dissappointed to say the least.
When I was there, the hotel had arrangement with two diver operators. They even had a watersports building on site (far side of the pool) that they taught scuba classes in, but no boat operator on site. Pelican (now owned by Unique) had a booth in the lower lobby you could book trips through and the concierge would book them for you at the front desk area also.
Unique is the closest operator. They are on the other side of the hotel next door at the pier. maybe a 1 minute to two minute walk. There is a paved/boarded walkway between the beach and all the hotels that interconnects all the way down the beach. so easy to roll a "rolling dive bag" between the hotels. I've not really heard anything bad about Unique.
I used Pelican over near the Holiday Inn. They were a good operation. Unique bought them out a couple years ago.... but I think they still operate out of both locations.
Other dive operators all have positive reviews except two.. (Mermaid Divers & Red Saild. search around and you'll see lots of negative reviews of Mermaid on many different boards. Red Sail has bad reviews of being a Cattle Boat operator and fed from the cruise boat lines.).
as for hauling tanks.... tanks are included in all the dives and are typically waiting for you on the boat when you arrive. I'm not sure which do nitrox or steel tanks. I think that maybe Dive with Clive does. If you don't want to walk to the dive operators, all of them have free pickup, but it's typically on a set schedule. (I missed the shuttle one day and didn't have time to walk and had to take a cab for example.)
Hope all this is helpful.
mike