We used a third first class award when we traveled SBP-LAX-BOS-LHR-NCL and NCL-LHR-LAX-SBP two years ago with my daughter (just under 2). The NewCastle flights were BA (Business Class) and American Eagle San Luis Obispo flights were Coach.

Although there is a lot of room in first, it was nice for her to have her own seat to sleep in.

-Mike