You are getting some great advice from some folks in the know.
I love the "timeline" pointing out how GMRS/FRS has evolved. One respondent mentioned MURS positively, and another mentioned the vast importance of good/better antennas.
Perhaps you could try MURS, and at the campsite you could have a better antenna system to reach out to the portable radio.
MURS radios could be used with a cheap, home-made ground plane, and if it could be elevated even a dozen feet in a clear spot should make a real difference. You could also use a mag-mount antenna on the vehicle, which would still be far superior to the little stock antenna on the radio. Another possibility are the telescoping or 5/8 Wave antennas made for 150-155 mhz by Smiley Antennas. I got the telescoping one as a gift for a friend who has the Baofeng (legal) MURS-only radio for farm use. It made a big difference, but is quite heavy and ungainly on a portable....in his case it is used with a legal Dakota Alert base MURS unit and he stayed with the stock antenna on the Baofeng MURS.
You could equip both radios with the 5/8 WL Smiley duckies too...even one on the campsite unit could make some difference. If I recall correctly, they are 9" long.
MURS is typically very quiet in most places, and has very good signal performance in wooded areas. I am sure some of the wise people here could recommend some good field-expedient solutions for improving the campsite end of the comms chain.