Sorry for not responding personally, but wanted to at least get the story out, since some of you haven't heard, and I didn't post much on FB.
SWA flight 1245 left Orlando at 4:50 on 9/7 (Labor Day). Shortly after takeoff, an alarm went off in the back of plane, and the pilot announced we would be landing in Tampa to "check things out." We were told to stay in our seats, since we'd most likely be taking off again shortly. We were also told that we would be greeted by fire trucks, but that was just protocol. We landed around 5:30, and were surrounded by fire trucks (more than a dozen, according to the local news). A couple of guys in silver suits (fireproof, I'd imagine--more than what the usual firefighters wear) approached the rear of the plane inspected it, then went back to the trucks.
At that point, we were told that we would be "evacuating the plane immediately, using the emergency slides at the front and rear exits. Do not take any of your belongings with you--just cross your arms and jump." We did (ds yelling "wheeeee!" all the way down the slide

--after all, he'd just spent 3 weeks at WDW riding malfunctioning service elevators (ToT), out of control railroads (both BTMRR and EE), and space shuttles encountering meteor showers (M:S), so an airplane slide was just like another ride), and then herded together on the tarmac for the next 30 minutes. Shuttle busses then took us over to the charter terminal (where the Tampa Bay Buccaneers fly out of, for you sports fans), where we were held for another 45 minutes or so. Finally, we were brought over to the main terminal in groups of 15 or 20 and were allowed to reboard the original plane to retrieve our personal belongings, then placed in line to board a new plane.
That plane took off around 7:30, and landed in Denver 3 hours later. Those that were getting off in Denver got off; those that were going on to SLC stayed on board; those of us destined for the West Coast deplaned and were placed on a plane to Las Vegas. We arrived in Vegas around 10:30, were given our new boarding passes for the following day along with hotel vouchers, and were shuttled over to a Hampton Inn for the night. The following morning, we returned to the airport and left around 12:30 pm for Portland (with a stop in Sacramento). We arrived in Portland around 4:30 pm--approximately 24 hours after leaving Tampa. 6 airports in 5 states in just over 24 hours--must be some kind of record, lol.
Seriously, we're fine, the kids are fine (dd got a little upset on the tarmac, but it turned out that was because she thought she wouldn't get her cell phone and ipod back

), and at least it happened at the end of the trip instead of the beginning (because missing a day of school is nothing, but no way was I gonna miss my Boma ADR, lol).
Sorry to leave you in suspense--I guess I just assumed everyone had heard about it (because it was about ME, and the world revolves around ME, doesn't it?) and knew that everything was okay. Here's a link to the news story, for those who want to hear the official version:
http://www.wtsp.com/news/local/story.aspx?storyid=113016