I started giving my DILs and sons a combined Mother's Day and Father's Day gift. One year I got them Garrett's popcorn and Fannie Mae chocolates, this year I ordered a gift box of Girl Scout cookies. I used to gift separately and give the girls a pot of flowers for their porch and the boys some BBQ spices or such.
I've made it a point to tell them that since they're parents now they should celebrate with their kids. My mother always said the same for me. In fact, the day before she died was Mother's Day and I was visiting her in her rehab facility. She wasn't feeling well and after about 30 minutes she told me to go home to my own kids. I stayed because she wasn't doing well, but I appreciated the thought.