Don't let Adobe make any decisions (don't use "Choose paper source by pdf page size")
Manually assign every page in the driver, so whatever is the most common size/tray, set it here
Then scroll down to the mixed media stuff and start with the other pages via New Page range
Then just fill in the changes and pages (individual pages are separated by a comma, page ranges by a hyphen)
Click Add definition to apply them, and when complete, select Close
Ther eis no better way, and really no simpler one, while Choose paper source by pdf page size is far simpler, it just won't be able to do odd sizes, nor can it do simplex vs duplex