What is a 172SH? I'm guessing you mean Skyhawk. You'll confuse people if you write it like that though, as usually the model number is the letter after "172" - eg a 172N or a 172S.
To actually carry 4 people and gear and fuel, you're looking one level up from the 172/PA28 range; a C182 is a nice choice. I'm don't know much about the Piper range...