I'm pregnant, what are some fun, healthy activities I can do on mother's day?

Outdoor activities. You can do almost anything you would like that doesn't involve a high likelihood of falling or getting hit in the belly. You could go for a walk, go to a zoo or botanical garden, go canoeing. Depending on the weather where you are, you could plant a vegetable garden. I do the race for the cure every year since it falls on mother's day here.