Speaking both as a daughter(-in-law) and as the mother of adult children, it depends a lot on the recipient. My MIL received a spa day one year and hated it; I wouldn't have minded it, my SIL would have loved it. OTOH my MIL loved the hand-decorated plant pots we gave her one year, which would have been a pointless gift to me.
I would love a class for something I'm interested in but don't know how to do--stained glass, Indian cooking, flower arranging, pysanky. Bonus if it comes with some basic supplies to keep going on my own. I would also enjoy a visit to a historic house, a concert, maybe an aquarium. Those things can be tough to schedule, though.