I'd suggest wearing block heels!! They're very comfortable, and give you much needed support when walking on a grassy area! They don't sink into the ground either like stilettos or pumps would!
You can literally type 'block heel sandals' into google, and it will pull up tons of styles to choose from! I've even seen some that are more bridal, and with a little sparkle. If that isn't your style, there are neutral colors as well!
Fortunately block heels are in right now and you can find them in many styles and heel heights. If you want a basic nude block heel you can find them inexpensively on Lulu's. If you really love the bedazzled statement shoe look you are going to have fewer options with a block heel compared to a stiletto.
I wore a short basic nude block heel for our outdoor ceremony and they were super easy to walk in on grass, gravel, and dirt.
They also sell these little caps you can put over skinny heels to give them more surface area so that you can walk on grass. I bought some but have never tried them, and some people say they work but others say they slip off or can damage your heels.