Add three bagels to whatever else you planned on eating?

It's hard to say what your caloric needs will be. I'm not sure what the basis is for 3,500 calories, because it will vary a lot depending on total weight, riding speed and total time, and your base metabolism. There are online calculators for base metabolism and calories burned while cycling. This should give you a ballpark of what you need, but I think once you get on tour you'll end up adjusting on the fly.