The best food is in the CPs. They pretty much always include breakfast, and most will do dinner for a reasonable price as long as you ask. IMHO the food in the casas is better than the food in the paladars. But, like others have said, Cuba is not a foodie destination, so keep your expectations low.

With 4 of you, hiring a driver will nearly always be cheaper and more efficient than taking the bus. If you don't book in advance, most of the time, your casa owner can arrange this for you since most of them have regular drivers who they work with.

Internet is limited in Cuba, so most arrangements happen on the ground, by phone or by lining up at ticket offices. Try not to stress about that too much; they're pretty accustomed to it, and heck, before the internet, we all used to travel that way anyway. Remember?

If you like culture, music, scenery and history, I'd put in a vote for the coastal city of Trinidad. I know you hadn't mentioned it, but it was my favourite stop in Cuba on my recent trip there.