Ditto on the congratulations, Tom! Mine are now 17 (daughter) and almost 15 (son). Seat problems never existed for me, since I've always had some four-seater Triumph around (Mayflower, various Heralds, the 10 Estate and Standard Pennant)!
Funny, just last night I came across some "baby" pictures, including one of a then-three-year-old daughter watching her then one-year-old brother. Today, as my daughter and I were riding around in my Herald sedan, we were discussing which of the "barn" cars we might fix up for her (emphasis on the WE, since she really wants and LIKES to help). My son loves to be driven around in the Herald and might even like to have one, but he's expressed little to no interest in the restoration/maintenance side of things to date. Maybe that will change when he gets closer to driving age!?