I made my mom an herb garden in a pot last year. Also a salsa garden (tomato/pepper/cilantro) would be good, or a salad garden. These are not directly paleo but are at least a healthy alternative to candy.
I hope it's ok to plug this here, but one of our own PaleoHackers (akd) has started an all-natural skincare line and her products would make awesome paleo-friendly mother's day gifts! (think coconut oil, avocado, and honey-based lotions, balms, scrubs, etc).