First time poster from Gran Canaria (formerly United Kingdom), thought I'd chip in on this one.
I've seen Tavares a couple of times live and watched a lot of footage... I would be a bit uncomfortable on using even a late second on Tavares. While his stats this year have looked impressive, it has to be taken in the context of the competition he's playing against. GC is not a major force in Spanish basketball at the moment and I think his inexperience would be badly found out in the NBA.
The best case scenario for Tavares would be a Manute Bol type of player - although with good coaching could become a little bit more than nuisance value at the rim.