I need help wording a wedding reception card to be mailed with the invite for a casual backyard wedding. ?

I am getting married this summer in my uncle's backyard in a beautiful area. We want to let our guests know that the attire can be relaxed (as in shorts and sandals with dress up shirts for guys and summer dresses for the ladies). We also need to strongly encourage the ladies to wear flats because the yard is made up of uneven stones, pebbles, and grass and we don't want any accidents. Lastly, there is a huge art fair that happens just a block away from ny uncle every summer that will be going on during our wedding. We need to stress the importance of the guests arriving in time to find parking and to carpool whenever possible. I've got my work cut out for me!!!