i would split the loads on the trucks, split the food 5 ways and have the passangers in each truck pay for the gas if they take turns its not that expensive and owner of the trucks pay for the 1st tank of gas if its only 3/4 full when you start o well its still your truck that is getting all the wear and tear on it no theirs .

when we go there are 3 of us in our truck one guy pays the gas on the way out I pay it on the way back and since its dads truck he doesnt pay at all we split the grocerys 3 ways and since the tent is half mine half dads we come out even on that and the 3rd guy gets a free tent no big deal we all have our own cots and personal gear this seems to work out very well for us if those guys dont like what you decide to do leave their a$$ in MN and take some people from here you already have it in wrighting that they will pay