Of all the locations we go, Zion is a standard location for us to visit. My father retired several years ago from the fire department and moved out of Southern California to the mountains in Southern Utah. We take the annual pilgrimage to see him every year. We love taking the side road through Zion because of the wonderful scenery and simple hikes the kids can handle.
Of my favorite hikes, there is a very specific one my wife and I absolutely love doing. Unfortunately, parking is a total pain in the ass. If you are driving up through the main road and entering off the 15 freeway heading towards the tunnel, you can see the overlook from the bottom of the canyon. It’s fun to see it with the kids before entering the tunnel and to tell them “we are going to look from way up there” and watch them process the information.
This photo here is the view point from the bottom. Stopping here and checking out the layout is pretty fun. It gives some amazing vantage points and in the winter months has some great ice formations so your personal princess elsa can appreciate her ice magic.
I would like to call out that our van is a 170″ wheelbase Sprinter in a 4 wheel drive with a roof rack. So those of you worried about clearance issues will be fine with most sprinter vans. Here is an image of our van for comparison. We were able to make it through the tunnel without an escort and without any issues.
Once you get to the top of the tunnel, take a chance to park anywhere you can. This screen shot of google earth shows the trailhead. Please keep in mind that toddlers are very difficult on the trail due to several danger areas. There are several areas that are single track and extremely steep with danger of falling. Use your judgement based on your comfort and ability level. 
The red circles show where to park and where the final lookout is. You can easily manage the hike with small kids as long as you can control them on the steeper sections. I caution you to use your personal judgement regarding the safety of your family. I have taken my kids on this hike a few times and they have done exceptionally well.
However, from the top of the trail at the actual overlook, this is what awaits you – 
these are actual photos of the trail, so be aware that there are not any safety rails for your children. If you feel comfortable assuming the risk, the view is amazing. We absolutely love Zion and our kids do as well. Note that in this last photo you can see the road at the bottom of the canyon. That is the turnout where the first image was taken.
