You do NOT need a “Ham” license to use a GMRS radio. That’s a whole different thing.
GMRS (General Mobile Radio Service) requires an individual commercial license ($70 bucks and not worth it for this exercise), uses the same frequencies as FRS (Family Radio Service) BUT GMRS is allowed to use more power in their transmitters. Think a small business with a few service trucks in one city area.
FRS = no more than 2 watts
GMRS = up to 30 watts
You can legally use a 2-watt FRS walkie talkie on GMRS channels with no issues. Most of the FRS walkie talkies include GMRS channels and that’s OK because they only operate at 2 watts. If you interfere with a GMRS commercial user (like Stan and his commercial freezer/cooler business for communicating with his trucks) then just switch to a different channel. That’s all there is to it.
Just FYI, a Ham license gets you WAY more channels (many span the globe, unlike FRS/GMRS good for under 50 miles) and transmitter power up to 1,000 watts. Whole nuther thing.
Get a few FRS walkie talkies at Walmart, spread them through a caravan and you’re good to go.