One thing to be aware of in West Curacao with seniors is that there's a lot of steps at many of the resorts. For that reason Marazul, All West, most of the Lagun properties will have that problem. If you're looking for a house, although the Coral Estates properties are up the hill (nice breeze in that area) you can drive down to the dive/shop now - used to b 4 flights down from Habitat - which is now condos catering to Euro's fom what I've read.
Even though the Lodge KH is upscale, they have some good deals in the summer. From the resort down to the dive shop is mostly paved ramps but to get to the beach is about 20 steps.
I might look for something east of Willenstad. Some of those properties are also high on cliffs overlooking the dive site but there's at least one set of rental villas that have individual dive docks and are right on the water. Sorry I don't have the name but I would have found them on vrbo.com
The resorts in Piscadera Bay are all waterfront (Old Hilton, Veneto, Renaissance, the Marriott is scheduled to re-open soon. Although it was pretty vertical they had elevators from the room towers to the beach/pool/dive level. Most of the condos in that area are up hill across the street and behind the resorts. Nice view and breeze but we chose to drive down - steep hill to walk. You can see it on the Royal Palms condos website. PBay is a nice area, there's a seldom use convention center, several resorts, beach bars and a couple decent restaurants. 4-5 mins, north of downtown so you miss all the cruise crowd - they go south from the Megaport.
No reason to stay downtown unless shopping is a priority over diving. About the only place with a shore dive is ScubaLodge and they can't bring a boat in there afaik. Much of the rest of town is on the working harbor. We do the Surges at the Sunscape AI resort if that's of interest. I have not been there but know there's a shore dive and Ocean Encounters shop there.
OE might be a good choice for senior checkout dives also, they have the largest fleet,most locations yet are very safety conscious. We dove with someone else all week but to do their dolphin dive I had to show a recent logged dive on Curacao. Nice boat with a big swim step.