Last year, my DH, DS(3), DD(18 mos) and I went with our Dniece (our babysitter) and some friends. We don't buy souvenirs for people who aren't with us - because I think it's cheesy to bring something home that says where we've been and they haven't - unless there is something that I just knew would be perfect for someone. We sent a bunch of postcards to people from WDW and bought a bunch of stuff for our kids that they wouldn't be able to get anywhere else, like miniature ride vehicles. We also bought the all-you-can-stuff Mr. Potato Head items and My Little Pony items for $18 each, and we actually brought back a box for our friends' daughter's birthday. In total, we probably spent only about $400 for souvenirs, although we would have loved to spend more.
In previous trips (before children), my husband and I bought art prints, jackets, clothing and bigger items, but we only spent $500-600 per trip then.