Doing a mesh would hurt performance considerably at those distances. If you could, I would run fiber to a POE switch outside right next to the lawn, and give all of the access points a home run to that switch. Of course, your switch would have to have an uplink to your AP VLAN. I would not combine mesh with high density, when performance is needed. If it is not going to rain, you can use indoor APs with those AP mounts on a temporary basis. I would not put indoor APS outdoors for an extended period of time.
Attached is an example of what was done for a temporary event outside. We put the switch in a larger plastic container to protect it from any incidental moisture (do not do this when there is rain), and ran ethernet cables from the switch to the individual access points.