In my most recent game as Mehmed II, I mostly beelined Gunpowder and had to backfill a lot of standard early techs. But you don't have Alphabet yet?! Wow.
As to your question, is he in a current state to be useful as an attack dog now? If so, would he be after you take those two cities? If Yes and then no, I'd say take the deal. If he's not useful now or he'd still be useful after, go ahead and take the cities.