Hey Bluesy, going on other quilted maple kits the veneers are very thin, so I would do very minimal sanding and with at least 320 grit or higher. Not worth risking sanding through the veneer.
If you are going to pop the grain with a darker colour then certainly no pre-sanding before the dark coat.
Might be safer to do a very light sand of the veneer and go straight down with the stain colour of your choice