Annetta, many suggestions have been given for making the patch and how to make it re-stickable. I have heard patch attach is a very good product, but have not used it.
Grandmas are sometimes asked the impossible because they are so 
I am wondering - how many times can the patch be "re-stuck" and will it stay stuck?
How do you protect the back of it when it is not in use?
How many items will this be on?
Would it be better to have duplicates? If not, show him how to hand stitch the patch so he can remove and replace it as often as he wants.
Let us know how this works out.
Have a great weekend.
Pattiann