We are using their air for the first time soon also, so I don't have much experience with this. From scouring these boards, I think the answer to your question is 'no,' you can't reschedule it once it's booked.
We thankfully got a call from them before they booked ours because they had a challenge booking our itinerary and wanted to know which of the two available options we wanted to do. That was a blessing, because we at least got to see the proposed itinerary before it was set in stone.
Once they book it, however, I believe you're locked in.
But, as with anything else, it never hurts to ask! The person who contacted us was a "Revenue Air Coordinator," so perhaps you could call the general number and ask for that department. Best of luck to you.