For CAN Bus and UART lines, just don't worry about the trace widths as you'll be complicating things for yourself.
Place the IC as close to the connector/terminal as possible, having the CAN-related pins facing to it. The idea is to keep the traces between the connector/terminal to the IC's CAN-related pins as short as possible.
As for the trace widths in general, I'd make them same width as the width of the suggested footprint pad width.