There’s another tax advantage unique to the 529 plan.
There’s no federal gift tax on contributions up to $16,000 per year for single filers and $32,000 for married filers.
There’s even an option to gift amounts up to $80,000 for single filers and up to $160,000 for married filers if pro-rated over 5 years.
This means you could make a one-time gift equivalent to the 5 year amount and it could all qualify for the federal gift tax exclusion. Consult your tax advisor.