Tricky situation: one companion has significant mobility issues, another (the photographer) is going to want to get out and go some distance away from the car to get the best shots.
Ireland's west is a photographers dream (I say this as an avid photographer myself who was constantly swooning in Ireland), but keep in mind that a lot of the best, most drool-worthy photos will require some walking (and climbing), in some cases across terrain that's far from ideal (and in some cases, impossible or at least very dangerous for those with significant mobility issues).
This is probably already on your list, but you will definitely want to include a stop at the Cliffs of Moher - it'll be one of the best places that will work for all members of your party.
Here are are 3 older threads that I think will provide some context - you'll see the dilemma...suggest you take a look, and I think you'll realize that the needs and preferences for your avid photographer friend may be difficult to balance against your mobility-challenged friend. At some point, the two companions may need to split up at least for a short while, so hopefully everyone is understanding and willing to accommodate the others' needs. Have a look (these posts include links with some photos that should be helpful in both understanding the terrain challenges, and also seeing some of the very compelling subjects that will make your photographer want to go wild).
West Ireland sights for seniors
Separate day trips to the Cliffs & Islands?
Puffins on Inishmore?
Shortcut links to photos showing some of the terrain/scenery/mobility issues:
Inishmore's Uneven Ground (click any photo for a larger view)
The Climb Up Skellig Michael (click any photo for a better view)
Hope that helps.