Friday is the new Wednesday
Is it one complete hike?
Yes, it's a 3 day hike if you do all the caches, with children I would add another day. If you like, you can spend the night at Erich hütte (near #16). In summer time, you should make reservations especially for the weekend. Only a few are along the main road. The rest you can only reach by foot. The trail is not hard, not very steep, so if your kids are in good shape and not too small, it won't be a problem to take them.
Do you drive to different locations and then hike?
If you want to be at home at night, there is a bus running on the main road and there are some parking lots suggested. The bus stops at those parking lots. You can get a schedule at one of the three information desks. The bus stops are on the map, indicated with an "H".
Can it be completed in a weekend?
Yes.
If you want to do all caches, my suggestion would be to do #1-10 on an evening. Then start the next day at #11. Walk to #17 and take the bus to #11, or skip #17 and spend the night in Erich hütte. The following day, you can do #16-#33 or #35 and return by bus.
The HKC contains 35 caches, but I only found 17 of those. When I found 14-15 caches, I was able to crack the code to collect the coin. It took me 2 days. Unfortunately I wasn't able to stay at the Erich hütte (full), so I did day trips and because I needed to wait too long for the bus, I walked back on the side of the road.
At the info desk they said that the night cache was needed to crack the code, but I was able to do without (but still went for the night cache). That is when you like puzzling and understand both English and German
In all, it is definitely a recommender. Good caches, no micro's and excellent views. I really enjoyed it, even in the rain.
If you have more questions, feel free to ask!