I did the Brighton Half earlier this year where the distance was decidedly out (official course length was adjusted to 13.4 miles) and I forgot to set my watch - the start was a bit fraught, I was late :-/ I could "feel" that the mile markers were out at mile 3 and 4 and but I trusted them and as a result I ended up getting my pace wrong and holding back the last couple of miles. If I'd had my Garmin set, I probably would have trusted that above the mile markers and paced myself better. You don't have to look at your watch if you've got it with you, but sometimes, it makes the difference...
We had a lot of fun, but we knew the boundaries - and if we didn't pay attention we were reminded very clearly, but no violence. I spent my childhood falling out of trees and building camps in the woods and being told that I could be whatever I wanted as long as I worked hard at school. I grew up to be good friends with both parents, and I value every moment with them - or did, in the case of my Dad because he died earlier this year.
Anyway, this isn't meant to be about me . Back to the question - what do we do about it as an adult? Use our own experience, I suppose... If it worked for us, then it has to be worth passing on.
I know what you mean about times of club runs - I'm a member of the Serpentine and there are alot of sessions I can't make because of work. It can be a real pain, but if you can't make it, one week, you may be able to the next. The club is really friendly and they really don't mind if you come for a few runs to try it out before joining, so there's no pressure to go