I assumes the sons were close to college age, so it may be too late for much potential tax free growth of investment money. But if they are just entering college, there still some potential (3-4+ years) tax free growth with the money in a 529 plan. It's not too late to contribute to a 529. 529 plan contributions may get a limited state deduction, but there is no federal deduction. The gift tax exception is only a little better.
There's numerous articles on the net. e.g.
https://www.fidelity.com/learning-center/personal-finance/college-planning/abcs-of-college-savings-p...
https://www.savingforcollege.com/intro-to-529s/what-is-a-529-plan
