Congratulations on your garden!
Ants are not particularly a problem in the garden. They do not eat living plants and their tunnels do aerate the soil.
Things that will keep them away include strong smelling aromatics like mint, tansy, etc or making a ring of powdery stuff (flour, talcum, chalk, etc) around plants you want them to stay off. They have a hard time walking over powder, clogs their spiracles.
If they are fire ants or for some reason you feel like you really have to get rid of them, pour boiling water down their nest.