With SW, you will want to check in when they begin giving out boarding passes usually one hour before departure. However, people start lining up to check in earlier than that. If it is important to you, to find several seats together, then I would arrive more than one hour prior. Check SW's website and see what they recommend for the airports you are using.
We just got back from WDW and we flew SW from Kansas City, another small airport. Left on Monday 4/8 and arrived at airport 2 hours before flight departed even though on SW's website it recommended 1 1/2 hour arrival prior to flight time. Curbside check in was a breeze as was going through security. I must commend the security in Kansas City. I thought they were doing a very thorough and efficient job and I felt very secure.
When we left for home yesterday I had it in my mind that we needed to leave WDW at 2:30 for a 4:10 flight when I really had intended to be at MCO at 2:30 because SW also recommended arriving 1 1/2 hours before departure in Orlando. I don't know where my mind was--maybe not wanting to leave??????? Anyway we pulled into the rental car garage at 3:00 p.m. Checked our bags at curbside with no line. Inside at counter, there was a long line. Went through security (I was even wanded.) and checked in at SW gate by 3:25. Of course, our boarding passes were #88 and #89 but we just went and sat in line for the third boarding group so we didn't have any problems finding two seats together.
I wouldn't recommend cutting it that close though. When I finally realized what I had done on the drive to the airport I started getting a little antsy. I really feel that following your airline's recommendation is sufficient. If SW still recommends arriving 1 1/2 hours at both of these airports when we go in May, that is what I will do--providing I don't lose my mind again! LOL.