I send them home at the end of the day before Xmas with there parent's. I like the idea of opening things under the tree as a group regardless of age, but its a tradition for my family to open any and all presents on Xmas morning so I actually get a little upset if my kids gifts are opened early or if someone opens the gift a week before Xmas or something. The only exception is at our Xmas Party but Santa gives the present to each child so its a little different. Each to their own and I think it's a very personal thing.

For birthday's I never allow the gift to be opened here. Theres only one gift and while it will teach the kids to share and observe another recieving a gift on their special day, it's just a conflict that I can totally avoid if it's sent home.