Your welcome! The preorder code will stay in your account until you actually order the cd and checkout, so you can edit the pics ffrom your first trip and then if you don't think you have enough you can just let the pics expire. Also, if you think you would like to do it for both trips, you can have more than one credit in your card at a time (at least that what I have been told by Photopass customer service).
The best thing anyone can do when they preorder is hit up as many Photopass spots as possible, especially in front of the park icons. If the line is only one or two groups long, stop at all of 'em because you never know what the other guests in the background will be doing when you get your photos back. LOL! Also, be sure to take shots at different times of the day in the same places (like daytime castle and nighttime castle). On our last trip, we found a Photopass guy all alone off to the side of the castle and he kept taking our picture everytime the castle changed colors.

He'd say, "Wait! Now it's blue!" and "Nobody move! It's about to turn purple!"

We were all cracking up.
Here's a couple of my best tips:
First, be sure to write down (or take a pic) of any Photopass card #s you receive. This way, if you lose the card you can still retrieve your photos.
Second, at meet and greet locations, be sure to tell the photographer's assistant (or the photographer if no asst. is there) that you have already preordered the cd and to snap away! Some of the best shots we have are the interaction shots that take place before the full-on posed shot.