There are thousand of action/adventure movies that have a romance between two characters without having them retreat in some romantic place.

Actually, besides the Empire Strikes Back... any other adventure film has the main character get the girl while he is doing the main adventure (Indiana Jones, James Bond...)

I guess, if you want to make it a trilogy, simply make a first movie where they all meet, they all fight some evil, and Anakin gets "Padme" at the end.

LIKE ANY OTHER ADVENTURE MOVIE.

You dont need more "big plot" in the first movie. You shouldnt even have it. If you have all three main characters living an adventure on the first movie, all of them together, helps you stablish that great friendship they have.

Then, on the next two movies you can develop the plot.

If you think about it, Han and Luke almost dont spend any time together during the OT, just on ANH. And they feel more like friends than Obi Wan and Anakin.

The problem with the prequels was that on Episode I, the three main characters didnt interact with each other, and then, by Episode II the three of them where totally different characters!

Its hard to see on the Prequels a shot where you can see Anakin Obiwan and Padme together (besides the beginning of EP2, the Arena, and Mustafar, i cant think of another)