My Sister is disabled as well and she loves crafts...
One year I got felt and made a big christmas tree wall hanging... then I took in all sorts of smaller pieces of felt to her... she and I glued together ornaments and such and decorated her christmas tree (works for easter and fall time as well)
Yarn baby balls work on dexterity ... you cut a cardboard donut and then wrap yarn around through the hole and around the outside densely until you fill the hole then you around the edge... if you make small ones they are pom poms but are fun to hang as ornaments on a real tree. (I haven't done this in years so I may be missing a few steps)
If glass is okay... you can make swirled glass ornaments with just paint and the clear ornaments.
Salt clay is fun to make and endless possibilities to do with that... or you could change it up a bit and use gingerbread instead.
Chocolate covered Marshmellows... similar to the pretzels... but lots of fun to watch melt
~ also go well as christmas gift with a packet of cocoa... homemade or store bought ... (I just use a gift in a jar recipe for cocoa and put it into small foodsafe bags that can be found in the cake decoration section)
Fabric scrap garlands.... just take some rope.... and fabric scraps.. and at interval tie the scrap to the rope... and instant garland... and it looks rustic and cabiny too.
depending on attention span... large hook crochet can be alot of fun relatively quick to make scarfs and functional too.
Yeah I'm not coming up with much more today... but felt is always a good bet.... I always buy a bunch when it comes on sale each year to restock my stash of it... basically if you need an instant project create scenes or hangings with felt.... also good for making fabric postcards.