My sister just asked about the Nabi Jr tablet for her 2-year old daughter. My sister has no home computer or internet (not even dial-up), just an iPhone to share photos with the grandmother. I had to help them set up the family plan, these are their first smartphones, so neither of them are tech-savvy.
I consider myself pretty knowledgeable, and the advantages I can see for this tablet are durability (hopefully) and simplicity. For the price, I'd rather give her my old Nexus 7 with a beefy case, and buy myself a new one (with more storage). Since they don't have wifi, there is no danger of her accidentally spending money for apps or in-game (she wouldn't know anything about tethering). It's not like they would be able to download new apps to the kiddy tablet without wifi, same as if they had a Nexus 7.
Before I send it over, I can load it with a variety of apps and media to keep her entertained. With the remote download feature, I could send apps to the device for whenever she gets in wifi-range (library, coffee shop, etc.) I might be able to troubleshoot it over the phone, unlike an unfamiliar kid-oriented device.
Do you have other suggestions about why it would be better to stick with a kid-targeted tablet or more reasons to help me convince them that it would be better to give them my old Nexus?