Don't do more distance than a tank full of gas a day, i.e. 400 miles tops, any more becomes hard work instead of a holiday and the best laid plans of mice and men get in the way of rigid schedules, things such as weather and hangovers knacker up early morning starts.
4 people plus bags in a 172 is pushing things, best do it with no more than 2 so you're reasonably light and not arguing over schedules and trying to please everyone.
4 adults plus very, very light bags may leave fuel for something like 30 minutes flights. I t would be very hard to do the many fuel stops a day and definitely boring to have a day mainly at the tap ... 2 plus bags will allow full fuel.
From experience traveling with a non-pilot friend I think max. 2.5 hours legs, probably 250 miles a leg and two legs a day are nicely acceptable, if your focus is on flying. If your passenger is not addicted to aircraft, or you do sight seeing, I do buy the max 400 miles a day right away.