Hi,

Only my main character, a Nord Warrior is the Dragonborn of legend. But I have 2 other chars that are not dragonborn , a khajiit thief and an orc battlenecromancer vampire.

Would I have content for all of my chars in the Dragonborn DLC or just for the dovahkiin?

Thanks

You don't get the "start" for Dragonborn until you go partway through the MQ. I think it's at the point where you get the note from Delphine.

There is enough to do in Dragonborn for a non-Dragonborn. The Dragonborn main questline is short and a very small part of the DLC. Also, you don't need to start the MQ to go to Solstheim. Just talk to the captain on the Windhelm docks. For 250/500-ish gold he'll take you to Solstheim.

Really? Cool, I'll do that with my next character. Thanks.

You can do all sorts of stuff for Neloth, the elf in the giant shroom.

Everything is open to non-Dragonborns but the expansion's short Main quest, though there are a few quests that can't be done unless you finish said quest or at least go part of the way through it.

So, yeah, you won't be closed off from too much content if you're not Dragonborn.