I just looked up the Post Flight Report for a C172P I did an air test on last month.
I put down that with just me (180lb) and full fuel, I was at 1864lb, which was 81% MTOW - MTOW 2300lb I believe.
So, add in another 3 medium sized adults I'd have to lose 17 gallons of fuel to be on MTOW, which would give me 26 gallons of fuel. Allow 9 gallons an hour, and assume landing with an hour's fuel, that gives me about 1:50 airborne time.
Okay, my 10 miles comment was a bit pessimistic. You'd manage around 200 miles.
G