You say “grandkids” as in plural.
Don’t buy land. Land that has multiple owners or people who have a “financial interest” is also known as a cluster ####. It can only go one way: Bad.
I know so many people who have ended up with a giant sh!tstorm on their hands because they ended up co-owning cabins, hunting land, farm land, etc with siblings and other relatives.
The problem is that land is usually an all or nothing proposition. It is very difficult for one party to sell their share, when they want, for the price they think they should get, and without creating hard feelings and misery.
If you’re viewing this as an investment, then there has to be the ability to liquidate. Compared to a mutual fund, land can be very difficult to liquidate at certain times and it can take an extensive amount of time and money to sell it. Keep in mind that the liquidation costs of land can involve paying the commission of real estate agents, so 7% of the sale price gets cut off the potential market gain.
Buy a low-fee S&P 500 index fund and enjoy life. A mutual fund can be liquidated within minutes. The 529 idea is also a very sound idea, but obviously that has a specific purpose that has to be a fit.
Grouse