I think Jack's idea is good...it is something you can make yours...

like perhaps a laffy taffy pressed in her hand after therapy (because everyone needs a smile) maybe one at some other time....

you can buy a bag of the small ones (I used to keep them in my classroom for anyone that looked like they were having a day)

one placed in your son's hand to give to mommy

stuff like that but NOT OVERBOARD

the point is to acknowledge without pursuing