If your embroidery vendor could/would do Carhartt jackets, that'd be a good wheeling/recovery/field wrenching jacket. They're popular at our gun club.
Ideally, some type of trated nylon rain-resistant jacket would be good too (wheeling and rain seem to go together).
What's a "flex fit" hat - elastic?
Bucket hats would be good for summer (especially for us "north sea" complexion types who avoid the sun).
As mentioned, mechanic's shirts would be cool too.
A camo hat would also be cool - at least for me... Other good colors are khaki tan, olive green, grey, or anything non-white.
If you don't already have a vendor in mind, I can PM you with one we've done a lot of business with. Good quality stuff, and they do nice work - although not cheaply.