Until you decide if you want to go BIG I would keep it simple for now. By Big I mean another battery, solar/generator, and built in inverter. Here's what you can easily do quickly.
A coffee grinder is ~ 75 watts and our waterpik shows 34 watts. I doubt you'll use both at the same time!! : ) Walmart sells a 400 watt Cobra inverter with cigarette plug for $25 that you can simply plug into one of the 12vdc plugs in your camper. Then just plug your small devices into that.
Sears/Kmart sells a 120 watt travel inverter with built-in USB for $27. Another one is 150 watt with 2 120VAC outlets and 2 USB ports for $30. They are easy to find and pretty cheap.
I wouldn't spend the money for a pure sine wave inverter for a coffee grinder!! But that's just me.