Handheld GPS Unit Recommendation for Visual Corner Searches
Perfect fit for a Garmin. If he has diffculty seeing small screens go for the largest screen possible. I've reviewed the Garmin 276C https://buy.garmin.com/en-US/US/p/539722
If you need to do imagery, then stop and don't go Garmin - way too much overhead. If you must go imagery, try Free Avenza - pumping out georeferenced PDF with baked in symbology. works on any phone, but limited to 3 maps, unless you pay for pro. Avenza for imagery, Garmins for precise navigation to just points, the latter a lot less work.
The Garmin above is Spendy, but compliant with all basemaps (plenty useable at 1:5,000) especially in the lower 48. Alternative is the current line of Garmins, but they are smaller screens. Stick to buttons (78/64 series) for using in bushes with gloves, cold.
Waypoints are the simplest way to allow nav, so extracting all your points with a name can be blown into the unit (free Basecamp software) from CSV, or using the Free DNRGPS. If you can get your data to a shapefile (say in Lat/long, or UTM), then load into the garmin in seconds. Garmins know nothing about NAD83, so convert NAD83 to WGS84 using _5 or something more robust to shave that 1.5 meters or so.
Garmins for navigating are the best tool out there. The closest waypoint will float to the top of the waypoint list too, so you dont' have to worry about management there.
Message me if you want some documentation.
Used Thales Promark 3 and Mappers would be ideal and background maps can be uploaded to show and record waypoints, drawings, USGS maps and aerial photos and more.