Attire
"Dressy casual"; in general, anything more formal than a hike and more casual than a ballroom is perfect.
Note that events are outside and on grass. April here tends to be warm and mild. Plan footwear accordingly -- barefoot optional. Dress up for fun, but dress down for comfort!
Middle Earth attire is encouraged for those who are interested! Hobbits, elves, wizards, rangers, ents, oh my. If you dress as a wizard you will probably not be the only one dressed as a wizard.
A few sources of inspiration:
https://www.medievalcollectibles.com/product-category/clothing/
your local Ren Faire