Child safety seat laws are regulated by the states. Here is a state by state list...
http://www.iihs.org/laws/ChildRestraint.aspx. However, most are identical.
In our coach, the only seats that have shoulder belts are the captain's chairs in the front. The recliner behind the co-pilot seat will swivel to be rear facing or forward facing. You can place the child seat in either direction. My suggestion is, if you have the option, swivel the chair to face forward and install the child seat facing rearward for the infant. The todler would be probably be safest in a booster seat with the shoulder belt in place.
New government safety standards released last week, suggest that children remain in a rear facing safety seat until the age of two years. Here is info from the National Highway Traffic Safety Administration (NHTSA)
http://www.nhtsa.gov/ChildSafety/step2.
If you don't have enough belts, you may have to put Mom and Grandma in bubble wrap
