I would make a mash up for him for sure. Is that him in the picture? He looks great if it is!
My friend has an older gelding 26yrs+ and she gives him:
-1/4 cup beet pulp
-1/4 sweet feet
-1 cup seniors suppliment
All mixed together and then adds warm water and lets it turn into mash. She also adds some Flax Seed in there once again (I'm not positive how much of this)
She buys her old guy special hay that is very fine and not hard for him to chew as well.