Setup an email for your kids, send them emails throughout their childhood, include stories about them and the funny (and maybe not so funny) things they've done and said, pictures of them and their artwork, and life advice for them. Then, give them the password to check all of the emails once they turn 18.     
                                    

Want to build up your collection of Disney movies for your little buddies? The best and cheapest way I found was to join the Disney Movie Club. You get 4 or 5 movies for $1 and only have to buy a few in the next couple of years. The specifics seem to change depending on when you sign up, but it's worth looking into! When I had my commitment fulfilled, I cancelled so that I wouldn't get mailers anymore, and they offered me 4 more for $1 so that I'd sign up again...which I did! https://disneymovierewards.go.com/     
                             

Kohl's Cares is a program at Kohl's program that all money made goes to children's hospitals. Each season they get a new collection of books with accompanying stuffed animals. The books and the animals are only $5 each! So, if you wanted a Corduroy book with a Corduroy bear, or How the Grinch Stole Christmas with a Grinch, or Knuffle Bunny with a Knuffle Bunny? They've done all those and continue to put out more!  https://corporate.kohls.com/corporate-responsibility/Kohls-Cares-Merchandise                  

Dressup for less: Buy costumes for dressup and pretend a day or so AFTER Halloween!  Much cheaper.
                               

Display your kids' art, framed on the wall, and easily change it out as they make new stuff with an artwork display frame.