YOur son will be fine. It's a matter of what to bring and how to juggle everything.
1) Don't buy him a seat. You can carry him in your lap as a lap child. Just make sure to get an infant boarding pass at check in.
2)Bring a copy of the birth certificate just is case. I haven't had to show my children's certificates yet, but you never know.
3)Gate check your stroller and infant seat unless you are planning to carry him to the gate. The stroller and infant seat should be "free baggage" If you are planning to carry him (wear him) to the gate, then check in the stroller and infant seat with you luggage. Either way, try to have a bag of some sort to protect the stroller and seat. Some airlines can be rough and your stuff can get broken. This happened with me on a trip to Hawaii. Thank goodness Hawaiian airlines reimbursed me for the broken wheel. Only a few airlines will.
4) On take off and landing, nurse or feed your baby. If he is asleep, don't wake him up. The feeding will help his ears.
5)If you don't want to haul everything, there are travel sites where you can rent the equipment that you need. One such site is http://babiesaway.com I haven't tried them but I heard that they are good.
Good luck!