Christmas presents - one at a time or all at once?

[pippin_999]

At my inlaws house the presents are opened one at a time, 
except for one memorable year when we were visiting with my 
toddler son. 

Grandma put the  tree  with the presents underneath inside the 
playpen and figured all was safe from busy little fingers. But Ben 
reached through the bars and though he could not get at the 
presents, he did manage to pull off all the tags!

My MIL is a very organized person, the sort who has all her 
shopping and wrapping done by the middle of July, so she 
couldn't remember who was supposed to get what. We took 
turns opening presents one at a time and trying to guess at the 
intended recipient.

Pippin