I have never been sure which is better. If you open them infront of people you can risk your child saying "i have that"(even though you beg them before not to say that!) or having a disappointed look on their face (i have taught my kids to always say thank you, its great - but sometimes you cant hide that look on their face that says otherwise). You also might have the problem of younger guests screaming and wanting to open them and play with them (we had that before, so after they were opened i put them in another room).
If you open them in private you can avoid all those dramas but some people then dont feel like their gift was received properly.
What do you think???Which is better? Does it make a difference if the party is at your home or at a venue (ie maccas).