Do they still sell the pictorial souvenir books in the parks? I have one from my grandparents from the 60's and two from the 90's, which my kids love to look at. I would love to buy them a current one this summer.
I saw a few in the park last weekend so you should be in luck. Another fun idea is take pictures from your trip and make a souvenir book of your own, with pictures you've taken over the years. These can be made at a reasonable cost at a few sites I know of (Costco photo center seems to be the least expensive) so that's an idea. You should, however, have no trouble finding a newer book in the parks on your trip. Have fun