Is it possible to do a curbless shower? I'm not a tile expert, but to me that would be the No. 1 thing I would look for in an accessible shower.

Joe, do you need a tub? Or would a walk-in or roll-in shower work best?

I'm in agreement with wisco-girl. I just did a shower for an MS customer about 3 months ago.

A couple of items while I await your response, and these are geared towards a fully accessible roll-in shower:

1) Use a movable seat instead of a built-in bench inside the shower.
2) Grab bar guidance can be found on ADA sites. You can shuffle the locations slightly depending on your shower configuration and your wife's abilities, but their recommended locations are pretty good.
3) For the shower head, have a hand-held unit on a bar. Most bars are not certified for grab bar use, but there are units that are. I used an Alsons ADA handheld. Looks nice, and the vertical bar is an actual grab bar and the height adjustment is an easily manipulated lever. Use the longest hose you can find.

4) If the grab bars will not be screwed directly into a wall stud or solid 2-by blocking installed between the studs, I prefer to use "Wing-It" anchors. I can do chin-ups on those things.

Kerdi? From the studs to tile, you're looking at:
a) drywall or cement board, the seams between panels do not have to be thinsetted or taped. I personally prefer cement board (wonderboard or durock) but you can use regular old drywall. If using drywall I recommend 5/8" drywall.
b) thinset and Kerdi over the drywall or cement board
c) thinset and tile over the Kerdi
d) grout

With accessible showers, I recommend a deck mud base versus the Kerdi foam trays. You can use the foam tray, I simply find deck mud easier to shape to the shower sizes that I build.

If a deck mud base, I staple plastic sheeting to the floor. Then set expanded metal lathe over the plastic and tack it in place, just enough so it doesn't flop around. Pack deck mud and set the drain, with the proper slope (1/4" per foot usually) from the walls to the drain. Once the deck mud has cured, Kerdi over it, then tile.

If using a Kerdi Foam tray, thinset the tray to the floor, then kerdi over the tray. Easy.

Here's a Kerdi thread from a few years ago. This is Kerdi over cement board on the walls, and Kerdi over sloped deck mud on the floor. Might not be the same methods you chose to use, but it shows a few techniques.

Lastly, the curb. you need 2" of vertical drop from the top of the curb to the shower drain. Floor pitch needs to be between 1/4" per foot and 1/2" per foot. You can usually get an inch or so simply from the sloped shower floor.

So you may still need an inch or so of elevation at the shower threshold. You can do a standard curb with square edges, or a roll-over hump. The hump is sort of like a speedbump. An inch or so of vertical over several inches of horizontal, gentle enough to roll over in a wheelchair is need be.

There are also flexible "pop-up" curbs that can be glued to the tile at the threshold. They stick up a couple of inches, and being made out of flexible material they can be rolled right over. I'm not sure of their durability.

Anyhow Joe, more than you asked for. And you thought YOUR post was long. lol

Oh, and for grab bars, etc, look at a website called "grab bar specialists."

Thank you sailorgirl for the input. Mongoct, I think I am going to go with a shower, No tub. I guess a walk in, with a little ledge, my wife is capable now of getting in a tub, so I guess a small ledge will be fine. Why would you do the removable bench instead of a built in? I believe he will use the wall stud as an achor for the grab bars, he mentioned doubleing them up in the area of the grab bars. So its cement board or drywall, not green board? I think I will insist on cement board. Id rather do overkill on everything. I believe the installer mentioned a kerdi base, should I insist on a deck mud base? Just your thought on a frameless shower door or frameless sliders? And should the controls be on the entry side or the opposite side or is this just a personal preference? Thank you all for the help. Joe