Pace is a charter airline...they fly all the flights for Vacation Express. They bought out the passenger charter division of UPS 4 or 5 years ago I believe. They fly 737's and have a good safety record.
I would not hesitate to fly them if they are going where you want to go on the dates you want to get there. I have used them through Vacation Express without problems. They have never changed flight times from the published since starting service out of Louisville or Nashville....even when tickets were purchased several months in advance.
They do fly into/out of Sanford but for us at least the times have been good. The drive from Sanford is an easy one. My only suggestion would be if you are renting a car there, have one member of your party get in line for the rental car, while others get baggage...as the airport is small and most rental agencies only have 1 clerk working, so when a plane load of 150 people arrive and 1/2 of them need rental cars the wait can get long...if someone beats the crowd you will be fine.