I’m guessing what the therapist means by “adaptive skills” is how he manages to work around his cognitive and memory deficits to get by in the workplace, and other things he does to cope with day to day life. So while he may have developed these adaptive skills over a long period of time they still deal with the day to day.

Executive function on the other hand is largely involved with long term goal setting and planning on how to achieve these goals. Executive functions are also involved with inhibiting inappropriate behavior, which seems to me includes the lack of remorse or recognition of an emotional response (his or yours) to the change of plans around having children. Poor executive function is associated with ADD as well as a number of other psychiatric disorders.

So yes, it sounds to me that his choices and decisions are likely driven by these short term adaptive responses, and you are prudent not to trust them, at least not for "life" plans.