Based on all your replies, I went to the local airport and booked the tickets. Saved about $125 compared the discount den online price. Thanks all.

Should I enroll in "Frontier Miles" now? If yes, can I just enroll myself and claim points for this family travel - 4 tickets?

I also have the BOA premium credit. Will be booking checked baggage online (before travel) and get the $100 incidental travel credit.