No, no, no! You do NOT want to open a direct custodial account atFidelity for your grandchildren. Instead open a 529 College Savings Account, where all the money will grow tax-free for college expenses.
As for the investments inside the 529 plan, opt for the “age-based” plan where they choose more aggressive investments for younger children, and become more conservative as college gets closer.
Then keep investing regularly. These gifts will have real value in the long run. CallFidelity and the willexplain further.