Not sure where you live but tank heaters have come in handy for us more than once.
Outside BBQ and gas lines are handy.
Outside table that hangs on the BBQ rail.
Ipod/iphone adapter/plate to the stereo or maybe a sat radio if you like that kind of stuff.
Standard auto style 12v plugs if it doesn't already have them.
Specify and aluminum spare as well or you'll probably get the standard white wheel.
Other than that, I think you've pretty much got it covered for what I would order.
Oh yeah, one last thing; Tell them to NOT
screw a cheap white plastic paper towel holder into your cabinets.....