I don't own an HV but I've had a fair bit to do with them, and since no one else has replied I thought perhaps I would.
HVs are generally clingy and sensitive: it's their stereotype and I've seen it in action. They are very affectionate and sensitive dogs, but also energetic and rambunctious. Your DC should be plenty old enough to cope - we had a similar dog when my DC were young and they were fine, and adored the dog.
It sounds as if you've given good thought to exercise and that is great. Let the dog grow up before you start to run with it, though: people worry about dogs' joints and while I've never seen any science to support it, you might as well be cautious.
What you will want to do in the dog's first two years (and intermittently thereafter) is train train train. Vizslas, like all HPR breeds, are on the whole very bright, and also have prey drive, so training kills two birds with one stone: you wear out that brain (which makes the dog ten times easier to live with) and you have control over the prey drive. If you can nail loose lead walking, recall, stop and stay, you will have a dog you can take anywhere. You'll have a running companion you can really enjoy.
TBH your best bet with training is a gundog trainer or an HPR club. Loads of people who don't intend to work their dogs do gundog training, because it works for these dogs. Group training is also great for socialisation and self-control. I've personally seen the benefit of gundog training Vs standard puppy class in my own working-line dogs.
Last (but not least) check out the lines of any puppy you plan to buy. Vizslas can have a genetic disease called something like Vizsla polymyositis, which is treatable, but bloody scary, can be difficult to manage, lifelong and no fun for the dog. There is no genetic test for it, but you can see what lines carry it. On the same note, get the pedigree names of the parents of any litter you consider, and plug them into the Kennel Club's Mate Select tool online. This will give you the co-efficient of inbreeding (COI). A low COI reduces (though it does not eliminate) the risk of genetic disease and probably immune disorders in the puppies. When we looked for our last puppy I wanted a COI of less than 5% and was delighted to find a pup with one much lower. Mind you, the KC data for many breeds is not complete, but it is a start.
Wow, that was longer than intended! Good luck with your puppy-hunt and I hope you have a great running companion.