I started my daughter with a 2 line foil around 5 or 6.
A mountain board without straps is a great way to introduce your kid to traction kiting in the lightest winds and in particular is very nice because you can chase them around the parking lot more easily. Once they get the feeling of upwind and downwind then its time for the water.
Her next kite was a 3 meter Best Waroo which we flew on land alot but never took us in the water. We did use that kite to learn the basics both in a buggy and on a mountain board.
Next was a 4 meter Eclipse Nano. The nano is really a top notch kite for a kid to fly. Its very intuitive because it is stable in the air, turns fast, and generates grunty power easily. Most importantly is how well it depowers on the bar and falls out of the sky when she drops the bar which is a big confidence booster. I believe Epic has the Junior pro which should be pretty similar. If they still do that would be the kite I recommend.
We also used a 6m Flysurfer Psycho4. Although the depower throw is short, the foils just don't give the feeling of grunt a low aspect tube has. The kite has to fly through the air to get power so for a beginner its just harder. Also, when it does go, it would fly through the wind window faster and generate a bigger (scarier for a little kid) power spike that didn't last as long. So very hard for a kid to use that kite.
I can't comment on the Viron, but I'm not seeing any reviewes suggesting that it is taking people upwind under power, mostly a beefed up trainer kite. Seb says not powerful and I take that to mean no power. You want a kite that makes power, but also has great depower. My only experience with Peter Lynn Arc's was long ago, but that was definitely a kite that need to move through the air to get power so while auto zenith will be nice, it will harder for her to learn to make power.
If you like Ozone, you might also try the Catalyst in 4. Similar ideas in a kite. Easy relaunch, easy power, easy depower.
One issue is the bar. The chicken loop just takes up too much space. We modified a bar to place a wichard2673 snap shackle attached to a metal loop on the harness. The wichard is so much shorter this allowed her to use more throw in the bar. We also used 300# lines so small kite would fly better in the lighter winds we were using it. The lines are shorter (16 meters) because a little kite needs less window to move around and it prevents the really big power spikes of long lines. We also made the chicken loop line significantly longer so once the bar is dropped, the kite will depower maximally and fall fast to keep her out of trouble.
One issue with kids is their motivation and stoke and attention span may all be smaller especially related to kitesurfing. I would definitely go slow and not push them and make sure they are having fun. Also, when the kid comes, you will want to have all of your attention on them, so in the beginning make sure to bring them out in ideal safe conditions for them, not epic conditions for you. Spend a long time learning to fly in light winds and drilling safety precautions and learning to make power by doing stand-up/sit-downs and scudding.
Also, the judgement is not quite as good. I remember teaching her to ride in the buggy. Once she got the confidence to start riding faster than I could run alongside she was having so much fun with it until she blasted over a sand dune so fast she flipped the buggy. I think it was 3 months before she was willing to take it up again. Helmets are a must!
Because the infrequency of times that schedule, conditions, and kid-interest line up it did take my daughter a very long time to progress. Now at the age of 11 she is riding upwind on a 7m Ozone C4 and starting to think about jumps a little. She's very stoked about it, but its funny because she only wants to go when the wind is north because she likes the spot, but only if its warm enough for no wetsuit.