Waybeau--for the kind of skiing you're doing I wouldn't worry too much about tuning. Wax is probably the biggest, because it makes the ski easier to turn. However, if you're skiing hard, cold condition the skis will turn fine without wax. Where you'll notice a difference is when the snow is warmer and softer. As far as edges go it's the opposite--sharp edges matter more on hard snow, obviously. On my carving skis I usually sharpen them every few days.Less often on my all mountain skis, my powder skis have never been sharpened. One reason to keep sharpening is to prevent the need for a shop tune because the edges have gotten too bad. Sharpening means side edges only. Base edges are only set and sharpened after the base is ground flat and then not touched, except for gently removing burrs, until the base is ground again. As far as having bases ground--a heavily used carving ski maybe yearly, other skis less often. If a ski starts to be hard to turn it can be a sign that the edges are higher than the base, due to wear of the base. If a ski stops holding an edge even though you sharpen it may mean the edges are worn. Both require grinding and resetting the edges.
One thing that matters about edges is ability--if people are mainly sking beginner runs they're not on their edges, so the edges don't get dull and if they are dull you wouldn't notice. As ability increases the need for tuning increases.
It's cost effective to do your own waxing and side edge sharpening. Most people would have a shop do base grinding, structuring, and base edge setting. Filling core shots and base gouges next to edges are in between. Other base gouges can be ignored, or the bigger ones can be fixed when and if the ski goes into the shop for a base grind..
Summary--for now you can get by with minimal ski maintenance. Skiing is an expensive sport, especially for a family, and the money is better spent on things like gear--especially making sure boots fit properly and replacing skis as the kids grow, making sure they are warm and dry, and lessons. As ability improves and performance becomes more important, more attention to tuning will start to pay off.