Ryan, Lots of good advice here. Fellow pilots don't want to see you in an AAIB bulletin.
What I'd strongly recommend is that you do 10 hours on your own after you qualify. Then work out a route which takes about 45 mins ( or no more than an hour) that gives some nice views (a bit of coast perhaps). I have one of these 'round the bay' trips permanently embossed into my memory and I use it a lot. Then take out your girlfriend on her own and finally take out her parents separately, preferably in the aircraft you learned in. You are going to be under pressure so you want everything to be as familiar as possible early on and this approach makes for a stress free flight for everyone..
If they like it, then you can plan the longer trip. I'm a very docile pilot, but I've had a couple of people go sickie on me in the air. Thank goodness for my autopilot! An instructor once tipped me off to keep a bag in my kneeboard when taking first timers up.
Oh, and 4 decent sized people with baggage for La France - I'd go for a C182, but you'd need additional training.