I am dropping off a rental vehicle on Sunday morning with two toddlers, car seat, and stroller that I have to get to the airport. Our flight leaves at 9am. What time should I drop off the car, or can it be dropped off at the airport?

7am should be fine unlike the other people's advice they are very busy on Sunday mornings at the airport so TSA could take up to an hour to an hour and a half to get through it depending on the crowd I fly all the time Sunday morning is probably the worst day

Give yourself 20-30 min to get from the car return to the terminal.

You should drop the car off now or in the next half hour, then you can take the shuttle from the rental company to your destination terminal for your flight you have to take in account for screening once you get to the airport. I'm sorry on Sunday not today at least an hour and a half before your flight