I agree. Don't train them that secondhand is second best.
Giving new life to an item is a great thing for the planet.
If you have the wherewithall, it's pretty easy to make drawstring gift bags out of fabric, and handy for storing the toys afterward (don't use christmassy fabric).
Ask on Freecycle for boxes and bags, and put some toys inside multiple so they have to unwrap more than one thing to get to the toy.
Tbh we were the first grandchildren and used to get mountains of toys, as I see in old photos, and I remember very few of them. It was the rituals that stuck with me the homemade advent calendar mum tied sweets to, decorating the windows with some frost-like potion and stencils, hot chocolate, helping wrap gifts for grandparents, baking, popcorn, etc. etc. all of this was when we were well under 10 years old.
I will say the gift that has stuck with me for literally 50 years was a random cardboard box stuffed with inexpensive art supplies -- watercolors, colored pencils, scissors, paper, glue, glitter, ribbons, etc. along with an instruction book. I still have the book and I'm 59. The wonderment of opening that box was amazing.
Also a dress-up box with scarves, purses, fancy (old) tops, skirts, empty perfume bottles, costume jewelry, a few items of makeup, hats, etc. collected from the closets of various aunties. We LOVED that and it cost nothing. Could be housed in a little suitcase or carry-on bag.