We have the RNIB here. The phone they suggest is this one
$1 which has no caller id and lots of little symbols on the cordless handset.
Having said that, it looks like the manufacturer do do a better cordless handset that might do the job:
$1 so that's one to add to the short list.
EDIT: I'll look at phones that announce the number as well, didn't know you could get those. Then I'll just need him to wear his hearing aids!