Consider carefully the order in which you decide to register. If you feel/know that one event is likely to fill up quickly, you may want to register for that one first. This can be a bit of a gamble for popular events, and you might guess wrong.
So, if Buckeye is your “home” regional, then I would recommend contacting your RD to see if they are willing to hold a spot for you in the event it fills up quickly. Then, go ahead and register for Pittsburgh first. Reaching out early like that helps show the home regional that you aren’t running away to another regional and simplifies your registration process. They may say no, but at least you are making your intention clear.
Plenty of teams register for multiple regionals, as I’m sure you know. It’s important that you’re at the ready to register as soon as possible to give yourself the best chance at ensuring your spot at the events you wish to attend.
As for the prep, make sure that you’ve got things packed in an orderly way, and pack for both events at the same time if they are close together. I might sound silly and you might be thinking “oh, we’ve got the time, we can just pack again.” But, speaking from experience, it’s a lot easier to pack for an event, attend it, and leave everything still packed in your shop for the next event. It removes a huge headache (packing twice), and of course you can bring additional things to the second event if you forgot them or decide you need them.
At the second event, take advantage of your experience by flying through inspection*. You’ve already passed once, so you should have an easy trip through the second time. Speaking as an Inspector, please don’t tell your second event inspector “but the staff at <insert event here> passed us”, as that will generally not be accepted. But, since you would have corrected problems at the first event, the time to pass should be shorter at the second event, which means more practice time, a more relaxing day, and a fuller night’s sleep going into the first day of competition.
And, the biggest thing IMHO is to make modifications to the robot and to your play between the events. You can’t open the bag to make the modifications directly, but if you have good documentation or good CAD models, or if you withhold a part of the robot before you bag it up at the end of the event, then you can bring your “modification” as part of your withholding allowance* to your second event.
*The aforementioned comments about inspection and withholding allowance assume that the 2015 rules are substantially similar to the 2014 rules in these regards.