If they've never flown Southwest, the flyers might want to look into Southwest's boarding policies before the trip.
As mentioned earlier, all of Southwest's flights have "open seating", meaning that there are no assigned seats. Tell them to think of it like a movie theater: When they walk on the plane, they can choose any open seat and sit down. (Keeping in mind that if they take the over-wing Emergency Exit row, there are additional age/physical requirements to sit there) If they're among the first to board, it's like getting to the movie theater really early and having a ton of empty seats to choose from. But then as more and more people arrive, you have to start looking for seats together. (Worst-case-scenario is that they're the last to board and they have to sit apart from each other)
When boarding with open seating, they'll be assigned a letter/number combo, which will be printed in large text on the boarding pass. These are assigned A1-A60, B1-B60, C1-C[some number], essentially in the order people check in. (There are some frequent flyer and business fare flyers who will get the lowest possible numbers no matter when they check in)
When they call up their letter group, they just find their place in the line based on the numbers. So if they have A42 and A43, they line up with the "A" group and get themselves sorted between the people who have A41 and A44. (There are signs to help sort people out)
Here's a little animated thing that Southwest put out when they switched to this new way of lining up:
http://www.southwest.com/boardingschool
And yes, the boarding pass is all they'll need for the flight. (Well, plus an ID at the security checkpoint for all adults 18+) Paper tickets for domestic flights are almost never seen anymore. Everything is all Electronic Tickets (E-Tickets).
And because they have only carry-on bags, they can totally skip the check-in counter and proceed to the security line, and then from there to the gate. If for some reason they need to re-print their boarding passes when they get to the airport, there are often kiosks away from the counters specifically for people who need to print the boarding passes.
Oh, and as you've obviously already discovered, when an airline advertises a fare like "$79 one way", that's the price before taxes and various airport fees... But yes, the base fare is $79. (Cheapest flights I've *ever* had from New England were years ago, Providence to Orlando, $49 each way, plus tax. And I think I ever had a $100 voucher from a delayed bag on a previous flight, so the flight only cost me about $15 for taxes, etc)
-Rob