First of all, it may help you to just sit down and write out one of the major life events. That may help you to become familiar with your characters, their quirks or habits or personalities.
Second, think about what happens that propels a character from Major Life Event #1 to Major Life Event #2. To use your example, what happens during their courtship that convinces them they want to be married? Maybe it is something that one of them says/does. Do they figure out that they have something in common (good or bad)? (like "Hey, I'm a huge Boston Celtics fan too!" OR "Hey, my dad died when I was in junior high too"). What do they like doing for dates - is it typical "dinner and a movie" type dates, or do they prefer to go camping/skiing/rock climbing/volunteering at a soup kitchen/spraying graffiti on abandoned buildings...? Did something traumatic happen on one of their dates that caused them to get closer? (like, there was a holdup at the restaurant. Or they were on a date when one of them found out their dad died. Or they were in a car accident.)
You can tell the same story from each character's point of view. When they're in the restaurant and it gets robbed, how do they each react? Could be interesting.
Also, once they decide they want to get married, they have to plan a wedding. What does that reveal about each of the characters? Do they learn things about each other that they don't like? (i.e. she is a total control freak, he won't even participate in planning the wedding, etc.) Then there's the in-laws, which you can include in the wedding planning.
Third and maybe most important- don't get hung up on whether you are writing a novel or a screenplay. The most important thing is to write it. As you figure out your story, you will figure out if it is better served as a novel or a screenplay, but as long as it hasn't been written, it will be neither a novel or a screenplay. Get the words out, and you can edit them later. You can switch between a novel and a screenplay. You can write BOTH a novel and a screenplay and see what you like better. But you gotta write!