529 plans are almost all extremely conservative in their allocation. Over a 20 year-ish period you’ll have a time horizon to even out the ups and downs and will have a much greater likelihood of success investing in a straight SP500 index fund. Then you can help junior pay for whatever you want (college, housing, travel abroad) with no restrictions from a greater nest egg, even with the tax implications.
Whatever you do: create a plan and diligently stick to it.