Bill Emory, you asked for it. Here is my homegrown advice about backyard ponds. Anyone can add to it if you have better or conflicting advice.
There used to be many garden places around town that one could go shopping for pond supplies. However, the price undercutting by Lowe's caused many (if not all) to stop offering pond supplies and advice.
Phill and I have used Springdale Water Gardens to buy some fish and plants. The plants we have now are water lilies and are hardy in our pond as we have one section that is about 4 feet in depth. Water hyacinths are nice if you can find them on sale here in June or so. These are annuals in our climate, but are pretty as they float atop the water and don't need pots.
The fist (koi and comets) overwinter as well. We don't have an aerator or filter. Years ago, we set up a dry stream bed to which our downspouts off the roof lead. The pond fills in the rain nad oxygenates while it rains as well.
Make sure you have some aquatic snails. They eat up the muck and algae. Also, there are barley treatments to reduce the sludge and keep the water clear. These can be purchased as floating inserts or once a month powdered treatments.
As for kids falling in? Our middle child did once, but we were right there. One early problem was teaching the dogs to stay out of the water. Our current dog caught four fish before we trained her out of fishing as a hobby.
Generally, the fish and dragonflies keep the mosquito larvae from populating the pond. I have no evidence for this, but I believe that the dynamic flow due to the dry stream bed keeps the water from being stagnant.
We do not have a crystal-clear pond. However, we have set up a nice ecosystem with fish that breed, frogs, tadpoles (until the fish eat them all), garter snakes that catch a fish now and then, and a few herons that take a lunch break. The insects are abundant, which thrills our kids (and us, the geeks).