This is a show where all the kids, despite wide variations in age, get along well (most of the time anyway) and work together as a team. The moral messages are wholesome as well and do so without being preachy. A good way to give kids these messages without risking them turning off.
Although the pace is somewhat slow by today's standards, even by today's standards the pace isn't too slow. Moreover, when I watched as a kid in the 80s, I didn't think that the pace was either too fast or too slow- it was just right. As for teens not seeing the show's appeal, let me remind you that this show, during THE BRADY BUNCH craze of the 90s, was popular with teens and college students, perhaps more so than with younger children. So THE BRADY BUNCH has stronger appeal to teens than I gather you think. As for what you seem to imply that some will mind the wholesome tone of the show, I believe that its resurgence in the 90s occurred because it's wholesome, not in spite of it. And, while nonwhites rarely appeared on the show, the few nonwhites that did appear were always nice and portrayed in a positive light. As for what Stepheresa says about the overt focus on self-image, that's normal for teenagers. Moreover, that focus isn't not as strong here as it has tended to be on other shows that feature teenagers.
The only thing that you'll have to watch out for with younger children is the sexism (which is why I put the green light at 7 rather than 5 or younger). It's particularly bad in the early seasons. You'll just have to remind your children of the way people thought back then. And again, it becomes balanced as the series progresses, most notably when Marcia beat Greg in a driving obstacle course that the family set up.
There's only one other thing you should watch out for. I didn't notice this as a kid but did notice in adolescence, which I found a little disturbing. Alice was a female chauvinist. In other words, she seemed to like the girls better than the boys, as she talked more to the girls than the boys. I don't know if she really was or if it was just my observation. If she really was, was Ann B. Davis (who played Alice) more comfortable with girls than with boys, or did Alice's behavior come exclusively from the writers? If you think about it, you just might be asking these questions yourself.