That sir is the most important part about the sport. This is, after all, a hobby. To be in this sport for over 30 years now, that is what you have to fall back on. If it is no longer fun and your family is not pulling on your shirt on Wednesday, asking if they can go to the track now instead of Saturday, then maybe its time to step away.
Unfortunately, that can be the issue for people entering the sport. People are caught up in the results side, and what speeds you reach, and step further away from the real meaning of the sport.
Now, regarding class structure, the industry is moving more and more toward single engine categories. Why, because of the example you stated. It is becoming too costly to have 3 different engines for certain tracks you go to, or to make a certain weight. There is no magic formula to make engines equal, it is the nature of motorsports.
In your area, the Northeast Rotax Max Challenge is very strong, as is the Northeast Shifterkart Series. Depending on the age of your son, I’d look into those regional programs. Otherwise, keep going to the club track and enjoy the weekend with the family, creating your own ‘good ole days’