If you check bags, there is no limit for the size of shampoos, etc. It is the above plane that there are restrictions. Pack the baby food/drink separately (I used an insulated lunch bag), and when you put it on the belt, let them know that you have baby food/drink in there. Any Tylenol, liquid, etc. (unless it is a larger prescription that is needed), goes in your quart size bag and should only be 3 ounces. I have not tried to do this differently for the baby, as the sizes have all been under 3 ounces, but you might be able to if you need a larger size of something.
The main thing is to be reasonable. When I looked into carrying breastmilk back from a trip (I was pumping), the TSA information said that it had to be in proportion to the length of the trip. For baby stuff, they are usually pretty good, and when I missed some liquid or cream, that was even too big, they nicely put it back in my diaper bag for me and sent me on the way.
To make it easier for you while going through the airport, check everything you can, strollers and carseats don't count towards your bag count, and then you don't have to lug them through the airport. Also, wear your son if possible in a pack that doesn't have metal, then you can just walk through the machine without having to get him out of anything.
Good luck!