I am not one to buy lots of souvenirs, so my comments do not really relate to the shops at this rest stop.
What was impressive is the produce stand there, where the products were clearly directly delivered from local farms. The prices were incredibly cheap and could not be more fresh.
If you are staying at an apartment or...
You can get Okinawa souvenirs. here.
Local foods, salt, clothes and so on.
I enjoyed eating ※Yanbaro-Inobuta-So-ki soba (okinawan noodle). That was cheap but delicious, too much to eat up for me. You should share it with a few people or choose a half size.
※Yanbaru-Inobuta is an origin pork whici hybridized to wild boar and pork.
I came by to see what this place is all about. I like the museum downstairs, a quick walk through. It has a tourist information section if you are interested. Opens at 9am but restaurants wont open till 11am.