We usually put on a table, and open in a group after the cake. Kids love seeing the parcel they brought being opened, and it gives the giftee the chance to thank the giver immediately.

But I'm aware that this is a very culture-specific practice. In some other countries it is considered the height of rudeness to open a gift while the guests are there, and elsewhere it's highly rude not to open it on the spot. I think we just all need to be aware in this big melting pot of a country that there are many ways of doing things, and many different ways of being polite.