We're flying Frontier in a few weeks, two adults, a toddler and a lap infant. It's our first time traveling with kids. We have to bring the two car seats which I understand are free carry-ons; aside from that, how do we get the best bang for our buck with our baggage? We can travel pretty lightly but will need at least one full-size suitcase, I think.

Also, recommendations on whether to pay to book seats? We don't all need to sit together, but the toddler obviously needs to be next to one parent. How likely is it that we'll get seats together? One flight is a red-eye Tuesday morning flight and the other is a Saturday evening.