Travel Advice

Im looking for advice on travelling with baby. We are flying to washington, dc for an 8 day trip in a few months. Our little guy will be 8 months when we go and flying in our  laps. We are not renting a car - just planning on public transportation, taxis and uber once we arrive. Any other mom's out there taken extended trips like this? What is essential to take (since we are limited by flying)? How do you handle the car seat? We have a graco click connect and always use the base -- do you check the base with the seat or just learn to buckle it in?