J.T.
this is what i do.... i put away $30 each month for each child's birthday(we have 3). so, when their bdays roll around(ALL right at Christmas no less!), i've felt the financial pain all year, rather than all at once! but, i do almost all of my expenses like that. we don't have family locally, so i can't really answer that. but i know a lot of ppl that have large local families do a quarterly potluck gathering and celebrate ALL birthdays that fell within that quarter - one big sheet cake from costco or something like that with all the names on it.
anyhow, back to the money aspect... my older kids(5 & 8) know that they have $360 allocated to their bday. they can have a party, or a small gathering with just the 5 of us and a nice gift, or we can go "do" something... they've had parties and a smaller gift all but 2 years - those years we did 2 consecutive nights at a local indoor water resort(1 for each bday) with a bday cake. by the time we add up 2 nights, food, dog sitter, cake - we were prob a little over $720, but it's a mini-vacation for ALL of us, so i don't mind.