Given your wife's situation, I suggest diving some of the resorts - they're almost all on named shore dive sites and have easier access. Bari Reef is arguably the best - the most counted species of fish in the Caribbean according to REEF - influenced by the former shops naturalist and survey dives - we did one.
One nice thing about Den Laman is it's a flat property except if your apt. is on the 2nd floor. The shop, restaurant, boat dock and parking all are on the same level. As others mentioned, I have a bad knee so found it convenient to sit in the well where the boats tie up - one step down, put on my gear then giant stride off the side. It is pretty shallow though - my buddy hit the bottom. Besides the stairs next to their dock, there's also an easy beach entry immediately next door (20' away) at Sand Dollar's beach entry next door.
Byddt Dice by comparison has a lot more steps down to their dive dock. Or ladders over the ironshore to their house reef.
Also pay the $5 or whatever it is now and dive Habitat as a guest - they have a place to drop gear right near the paved ramp that leads down to the dive dock. From there you can access Cliff to the north which is a rough entry over loose rock if you try it from the Dive Friends shop there, Also you can float in over the LaMachca wreck off Habitat but you won't be too disappointed if you miss it...
As mentioned Dive Friends in town has a same level dive dock and maybe 3-4 steps.
I'd personally stay at Den Laman over the Divi but the latter does have the advantage of having HSA certified staff so they may be able to help with boarding. Also being in town puts the restaurants/shops within walking distance.
If you dive 18 Palms - the Plaza's house reef - it's a beach entry. But check-in at Toucan Dive on the south side and either ask them to haul you/tanks in their golf cart or drive out the main gate and back into the small lot that's the next left - it might say employees but you can park there. Walk thru the gate and 18Palms is almost immediately to the right - it's a 10min. hike from the dive shop.
One other thing to look for is sand channels at some of the shore dives - they break the ironshore and in many cases you're floating b4 you contact the reef. Otherwise you wife will have a lot of difficulty climbing up and then down over the ironshore prevalent at most sites - I did. Here's an example at Vista Blue a more advanced south site.
http://www.shorediving.com/Earth/ABC/BonaireS/Vista_Blue/c004508.jpg
I found Salt Pier an easy beach entry but my buddy entered 10' away and found the ironshore shallow. Short swim out to a very good shallow pier dive once you're floating.
Also this site has a lot of entry photos - a few are dated but you get the idea.
Scuba Shore Diving Region: ABC Islands
Two I'd probably skip are the Hooker and 1000 Steps - both are done as boat dives also.
