Consider buying an approved child restraint system (CRS) device or a harness-style system approved by the FAA. They are suggested because they are safer than sitting on a lap during flight.
Baby formula, breast milk, medications and baby food can be brought on board in quantities larger than 3.4 ounces. Everything will be inspected, but you won't be asked to taste anything.
Many airlines have restrictions regarding infants. Delta and Southwest, for instance, requires a doctor's note before they will allow children less than 7 days old to fly.
It's up to each airline to regulate children traveling without an adult. Delta and Southwest allow children as young as 5 to fly without an escort. American Airlines does, as well, and charges a $100 unaccompanied minor service fee each way.
Consult the airline to determine the age regulations for children who will need their own seats. Most airlines---including Delta, Southwest and American Airlines---require that parents buy tickets for children older than 2. A child younger than that is allowed to sit on a parent's lap.
Parents traveling with a child in a child restraint system are limited to where on the plane they can sit. Delta, for example, doesn't allow you to sit in emergency exit rows, aisle seats or any seat that is one row ahead of or behind an emergency exit row.
