We don't do one by one as such but it's not a free for all either.
I let the kids (and us if there's one) open presents at the same time from the same person ie they open gifts from us at the same time, they open their presents from each other at the same time etc
ditto we do this too.
we dont do presents other than a token box of choccies etc for extended family -just immediate and grandparetns - i post to my sister and brother and them me
how much have i spent -mmm not to bad got a trap $250, about $60 each child incld stockings......but then ds went and won $200 worth of toyworld stuff so #1DS will feel a bit ummm left out lol, i've made #2 promise to get #1 something cool like proper soccer goals etc etc