bmac,
I have ridden 3 wheelers, 4 wheelers, motorcycles, etc. for over 20 years. A few thoughts:
As kids, we always made our own trails through the woods. It was an adventure and something we enjoyed. Usually took and ax and machette with us for the day. I suppose it was a good sense of accomplishment and a great way to spend time with the friends.
Husquavarna makes a brush cutter very similar to a weed eater except there is a blade in place of a string. It's easier to work with because you aren't bending down constantly and the blade is actually away from your limbs. Just need to be aware of the direction of blade spin and make sure it always kicks away from you and not toward you.....
For younger riders, I believe wider trails are more dangerous than narrow trails. The wider trails actually promote speed whereas the narrow trails limit that greatly. If you are weaving through the woods on a narrow trail, there isn't enough room to pick up the speed.
Although I have ridden down logging roads cleared by dozer, I think an atv trail holds up much better if the ground is undisturbed by large equipment. The shallow root systems in place seem to make for a more durable trail. Once that shallow root system is removed, it's easier to create the ruts.
You will be fine either way you decide to go. Your kids will love riding the atv's.