Outdoor Education and Leadership specialist. Hiking, Backpacking, Camping, and Alpine Skiing Guide. Published Outdoor Writer.
I would go straight to Pokemon Go players and start digging for answers using broad sweeping questions such as, "What do you like about PGO?" and beginning to narrow from there. The book "Ask" by Ryan Levesque is the perfect tool for this research.
As an outdoor educator I know how difficult it can be to get people to unplug and engage in outdoor activities. Geocaching is a hobby exactly halfway between PGO and traditional treasure hunts. Participants use GPS enabled devices to hide and located "caches" usually in the outdoors where they can record their finds and swap trinkets from the cache.
You might do well to approach both populations of users and find out what draws them to each. Then, using that information, form your copy and platform in a way that uses their own language, problems, and excitement to convert them.
Let me know if you'd like to chat more, I'm always happy to help.