We have done a LOT of flying and this is what I have found: if you are buying your child a ticket, a car seat and stroller are allowed and do not count towards baggage. If you are not buying a ticket, some nice people will allow it not to count as baggage, but most people will count it towards your total. Call the car rental and find out if or how much they charge for car seats. Its usually been pretty minimal if any charge, although we have been unpleasantly surprised once. Since you are doing a family reunion, I HIGHLY suggest calling people who are driving, even if you do not know them well, and asking around if anyone has extra car seats or cribs, etc. EVEN if you are allowed to bring all these things, let me tell you, pushing a stroller, and trying to pull luggage, and two cars seats through the airport, especially if you have to make bathroom trips, the whole thing is a challenge. If you can get someone to bring these items for you, it is such a blessing. ALSO, if you have not traveled recently, most airlines will ask for your baby's birth certificate, especially if they are riding on your lap, so make sure you have that or something that shows my age, because once when my daughter was 22 months, we had a real battle because they said she was over 2 and federal requirements wouldn't let her on without proof of her age. Pack baby benadryl in case of ear trouble or fussiness (also, my Dr. told me recently, taking a sudafed before flying can really help prevent ear trouble in adults). We just bought a portable DVD player and it made our last flight SO much more relaxing (if you don't have one, ask your friends if you can borrow one, or most laptops have a feature that plays DVDs) One of the tricks that has helped me the most is, after you pass through security, buy water. We always pack snacks, and not drinks because you can't get them through security, but sometimes it is a LONG wait until they bring drinks, so a little something to hold the kids over really helps. Wear shoes that slip off so you don't have to struggle with lacing up while pushing a double stroller. Good luck, the whole thing can be a bit of a challenge, but a fun experience anyway.