For me it's between Mahomes and Kittle. I like Howard but everything I'm seeing is Sanders probably ends up getting more work by the end of the year if things go to plan.
I think Kittle is probably the best option here. Even in a 12-team league, you should still be able to get a capable QB, even if you get the 12th best guy on your list. I even have a soft sport for Mahomes, because I picked him up in keeper leagues when he started Week 17 two seasons ago and it's paid off big-time in a handful of leagues.
But, I really do think the smart move is to keep Kittle just because TE is so top heavy. In order to get a top TE you will have to spend an early pick and now you don't have to.