It is so easy to become overindulgent. My 2 sons each get three christmas gifts from me. They are elated. I started this when they were young so they don't expect a ton. For their birthdays, I try to limit it to one item chosen by me and one by my husband. Kinda cool that my husband gets to pick something and so do I. We bet as to whose gift will "go over" the best.
My parents get my older son one week of basketball camp in July (they contribute $50 toward the $90 fee and my son doesn't know how I add a few $$'s to it) for Christmas and one week of basketball camp in August for his birthday. He strongly requests this gift every year for the past 3 years. I love it because I think it is so much better to spend $$ on experiences instead of "things." My younger son is only 4 so he gets one or two gifts.