If one-handed controls are a priority, you could go for something like:
Menu/Pause: "Tab"
Accept: "Q"
Cancel: "E"
Movement: "WASD"
I think regardless, remappable controls is always the best way to go.
Also, there's no reason to abandon the mouse controls, just make keyboard alternatives for them and leave the mouse controls available as an option for those who want them. Not like anyone wanting to play one-handed is touching the mouse in the process anyway. Could also add a simple toggle to disable mouse controls in the keybinding options.