Kids are easily distracted, so if you point a phone at them it'll completely throw them off whatever cute activity it was they were just doing - probably because they now want to play with your phone. No such problem with Spectacles - and not only that, it means you can keep two hands free (not a small issue when one arm might already have a child in it).
The problem is that Spectacles are so tied into Snapchat that it makes sharing the output very difficult. Grandma and Grandpa are not going to use Snapchat, and I'm not sure Snapchat wants them to. You can, eventually, import into Snapchat then export single videos back out again, but they lose the cool display method for circular videos and look awful. I think they could shift some of these glasses with a little rebranding and a spin-off app just for importing videos into whatever destination you want. They'll never do that, though. Maybe if they finally declare it dead they'll open up the sync API, but I'm not holding my breath.
(this is a repost of an old comment I wrote a few days ago in case anyone is suffering from deja-vu)