First, I don't blame you for deciding not to drive.....my limit in a car is about 9 hours and that's not even with a 15 month old!!! I don't believe you'll need a ticket for your 15 month old. I think it's under age two is considered a lap child.....however, if you wish to buy a seat you certainly can do so. My family flies SW almost exclusively these days. They do not have assigned seating but instead board by A, B, and C groups and preboards. Since you have a child under 4 you would be a preboard candidate. If you are not eligible for preboards you must check in online within 24 hours of your flight
(even with preboard you should check in) and are assigned an A,B, or C boarding pass depending on how many have checked in before you. When you get to gate you are boarded according to your pass.....preboards, A's and so on. Some people refer to it as a cattlecall, but, I've never found it to be bad. Too bad you didn't decide a few weeks back.......you probably could've gotten Norfolk/Orlando for about $39 each way during the SW sale last week. SW is defintely the way to go for this trip and in the future. I have also found their customer service to be probably the best in the industry, IMO, anyway. I've had some bad experiences with gate agents and customer service people from other airlines. Not so with SW.....everyone I've ever dealt with has been pleasant and seems to really enjoy their job. Hope this helps and have a great trip. Wish I were going!!!