Because I'm so close to this story I think it's been hard for me not to write it as it happened, same goes for the other characters, in my head I know how they sound, so I guess I need to write them in a way the audience can hear their differences as well.
As first drafts go I'm happy with this one, I think I need to let this breathe for a week or so to clear my head and refocus.
As a first draft you should pat yourself on the back. IT'S WRITTEN. Lot of writers struggle to get that far. I appreciate that this is based on personal experiences. Unfortunately, real life often makes for dull movies. No matter how incredible, events must be altered to tell a visual story. That's why such movies often have "based on" attached. (Even reality TV is scripted as witnessed by the WGA reality writers' picket. Somebody has to script in the backstabbing and conniving so predictably quintessential to reality tv.)
A friend's wedding was an example of everything that could go wrong. It was like a train wreck which would have been captured on video if the videographer hadn't been stuck on the highway. As funny as these wedding incidents were (in hindsight, of course), they don't make a good movie--sometimes a Funniest Home Video two minute clip. Movie weddings go over the top with calamity.
Your experiences are humorous but not over the top. The truck spinning out in front of the Denny's came close, suggesting a "Planes, Trains, Automobiles" scene. For your script, ask yourself, "What would have made this situation worse?" Then drop your characters into it. Force them (through you) to find a solution. Rather than resolving each problem, stack them.
Obviously your friends will recognize themselves in the characters. Even so, you need to really pull out and magnify differences. How does B feel about the divorce in your movie? He comes across as cavalier. Was he already playing the field on her? Maybe she's playing around on him. That's a piece you can explore. Mitch comes across as clueless about women. You might alter his character a bit to be more the technogeek of the group. Brian seems to be the 'every guy' character. Again rather than simply making them cardboard, you want to highlight how they are different and can still be friends. Use their different strengths to get out of the increasingly bad situations they find themselves in.
You survived the real life experiences because they were tolerably bad. In the movie, you really want to put your characters through a grueling hell. And as a result, let them win in the end in proportion. They should get the girls who perhaps are hitchhiking back where the base is located. Two of the guys and gals in the back of the pickup, and one pair in the front. Closing with them laughing and driving past the Denny's. Then you flip to the scene with the manager inside.
Take some time to clear your head then get back in there. Really torture your movie characters, make them work to get the girls in the end. Shine a bright light on the incidents to cast deep shadows that make it a cinematic experience. In the end it works best as a comedy "based on" your experiences rather than "an account of" your experiences.
Be optimistic about this piece. It shows good potential. Now that it's out of your head, you can start the process of refining it.