A:Answer There are some that can work alone and will do mostly what an 8 year old would want or need. Those are great entry VR headsets and are reasonably priced, being about $300-$500, if you want a stand alone then get the Quest 2. Which is a stand alone and a good entry to VR.
If you want to enjoy it yourself and want an overall better experience in the end. You will want one like the Rift S or HP Reverb G2, would need a decent PC. The Rift S can be found for about $400. There are better qualities and better visuals than the Rift S out there.