Difficult route; kick the Mrs out for half a day and gather all the kids and grandma to brainstorm/craft/write something for her. All depends on the age of the kids ofc.

Write her a letter and describe what places you would like to visit with her/why you love her/the small things she does that make her special

Go work out with her, support her through the hard reps and motivate each other

Treat her to a homemade steak dinner if you have the funds? Candles and roses?

Make a post workout care package? A post workout drink, protein bar, lay out a comfy outfit for her to wear, give her space to shower and offer a foot rub afterwards?

Decorate the house (and don't make her clean it up afterwards)

It seems like gifts (giving and receiving) are her love language.