First Post here, lurking for some time, enjoying this site, very much appreciated!
I am Sound Mixer from Munich, Germany, Bavaria....you know "Oktoberfest" :-)
My Advice would be to fix the Lavs to the Go-Pro. You would get clean sound there.
Proper Windshield for the Lavs.
Forget about the Range for IFB.No Chance, simple as that.
Make them Happy the Next Day by Watching the DVD.
Maybe the GoPros can record with an external Lav??
Maybe you should buy a couple of Zoom-Recorders and attach them similar
to the GoPros, dont forget about Windshields. MP3 Quality should do your Job.
Zaxcom with internal SD-Recording would definitely be best.
Call Production to make those come to the Set ASAP.
Good Luck, best Wishes,
Albrecht Harms