Let me give y'all an important tip on coffee there :)
Back when I was planning my first ever visit to La Serenissima, I was inundated by unsolicited commentary from various friends, mostly moaning about how it is the most expensive and megatouristic place i Europe and canals smell and whatnot. Coffee at 15 euro a pop featured prominently in those anecdotes.
While some of the epithets might be true (as they are for any hugely (and deservedly) popular tourist places), all of the bad stuff is easily avoided with a little planning and some common sense. But on the topic of coffee, it's NOT really that expensive, and not even necessarily in the touristic places. Thing is, if you enter a coffee place and look around, you will be able to find a plaque or piece of paper stating terms of service. You will also notice that the locals, if any, drink their espresso at the counter. If you look at the terms of service, you will discover that an excellent espresso by itself would cost, I dunno these days, let's say 1 euro. However if you sit down at a table inside, your costs immediately jump +3-5 euros. And if you sit at a table *outside*, that's another 4-6 euros. (you may have to adjust numbers for inflation, but the idea is the same). And that's how you end up with a 15-euro espresso. There's nothing bad in that in itself, sitting at an outside table in the early morning sun at St.Mark square nursing an espresso is well worth it as a one-off experience, but don't let that be your gold standard or turn you away from the city.
As to the the food in general, the situation is a bit complex. It's not the food is *bad*. It's perfectly fine, if somewhat non-trivial to find because of the tourist-induced mediocreness. But it is also not exactly for everyone's tastes - polenta, fried sardines, chopped liver, all heavy with onions, etc. And also due to the island logistics of the place, good food is really expensive.
And do pay attention to the sweets! They are often amazing, and for a really tasty and surprising souvenir, do buy some mostarda di frutta! It's essentially a sort of fruit jam with mustard in it :)