flying from the US to Europe with my family. I stopped flying for business about 4-5 years ago so i'm a little behind on the various revenue enhancements, etc.

flights are on BA. layover in LHR. BA wants $90/person RT to select seats ahead of time. Is this necessary?

btw, we are flying with our minor child, so apparently at 3 days out they give us some sort of family seating priority.