Tell him about how playing online (on select games) can add miis to the streetpass plaza

show him that it works

Tell him that he can use a lot of online services that are now off, including Miiverse!

You already did the hard part of convincing them to softmod. You could drop it as a suggestion along with other mods :]

tell him that he can play multiplayer with you

Thank you; your suggestions have been taken into account :)