There will be a Nintendo Direct tomorrow (September 13th) that will give us some more details on that as well as some more games. The original stream was delayed due to the 6.6 magnitude Hokkaido quake, so now it will take place on Thursday, September 13 at 3:00pm Pacific Time. "The broadcast will last approximately 35 minutes, and will feature information about upcoming Nintendo #3DS and #NintendoSwitch titles".
In addition to this, they've also confirmed that system software 6.0.0 will release alongside Nintendo Online.
Joy-Con will be fully compatible with these games - but for those who want their controller input a little more angular, Nintendo's got you covered here. For individual memberships, one, three and 12-month subscriptions will cost $3.99, $7.99 and $19.99, respectively. I'm not actually excited for Switch Online at all so far, but I also don't play any video games online. So... Since there will be some games that won't be able to make use of cloud saves, for whatever reason.
Prior to this change, it is important to confirm that your Nintendo Account or your child's Nintendo Account is linked to the correct user.