Hi, I've done thousands of miles on adult kick-scooters over many years. There are no-car paths almost everywhere now in Europe. Switzerland's covered with them. Many are specially smooth-surfaced for inline skating. Get the SwitzerlandMobility app for all the routes.
The key is to roll cool and gentle and you can go to the ends of the Earth in total comfort. You get an iron butt and steely abs for free.
On downhills, if you roll slow and brake in bursts, you won't have a brakeflap-heating problem. It will cool quickly anyway if you walk a few meters.
Use 20 cm wheels as in the Micro. If your commute is bumpy, ask them for an inflatable front wheel. Note that if your commute is a steep downhill, inflatables roll slightly slower than the normal solid PU wheels, so it may be good for your requirement to have them front and back.
Micro is based in Küsnacht so easy to contact and their scooters are used a lot by serious users in Switzerland. People who mock kick-scooters should check them out on a funny new thing called the worldwide web and enter the 21st century.
Meanwhile is you want to get fitter on your next weekend or vacation AND discover that your kids actually want to come with you, check out http://www.fit-touring.com
- I'd be thrilled to answer any other points and even to advise on trailers for pulling your kit and saving your back.