If the kids are very young, it's going to be quite a few years before they would face any meaningful consequences for using old spelling vs. new spelling. What difference does it make if they get a 92 instead of a 96 on a grade 4 spelling test? (And what kind of stupid teacher would give them bad marks for using the old spelling?) There is a very remote chance that when they are writing a university entrance exam they might lose a mark somewhere, and that their chance of getting into law school was thereby lost because they happened to be right on the borderline: but you can't go through life worrying about that kind of thing. It is much more likely that by that age they will have fully understood the difference between old spelling and new spelling, and have no difficulty in using either one as appropriate for the situation, just as I'm sure you do.
We had a spelling change in Yiddish wish started in the 1920's and is still not fully entrenched today. I am self-educated in Yiddish and my library has books in three major spelling systems, and I feel much more culturally aware because of my familiarity with those three systems than I would if I had been carefully shielded from the "obsolete" systems. There is certainly no justification for throwing out our old books because of their spelling, because most of them are simply irreplaceable.
EDIT: I should add the disclaimer that I happen to be a spelling terrorist; I invented my own Latinization for Yiddish based on the German roots, which drives the YIVO (Yiddish Institute) phoneticists crazy. I'm also not a great authority for "what do you care what the teachers say" because I just got kicked out of university last month for arguing with the professors