I do this same exact tradition every year too.

I usually get them from the Hallmark store. I can usually get them for $10 to $20. A little more expensive but they have selections that actually have to do with them.
DS6 last year received a bookbag ornanment that held a picture since it was his first year of school. This year they have an ornament that has a little woodland creature beaver maybe

that sings "All I want for Christmas is My Two Front Teeth." since he lost his first 3 teeth this year.
DH just gets their superhero

ornament which I can usually get on clearance the year before during after Christmas sales.
But I also check out Target, Boscov's, etc. Since last year I was lost with DD2 I did manage to find her a puppy and little kid ornament at Target since we got a new puppy and she seemed to be his biggest fan. Suprisingly it was on an endcap with the stationary department far away from the hoilday section.
Hallmark is my first stop though since they seem to have "occasion" ornaments and then I go from there.