thanks everyone for your thoughts... lots of things too think about.
Wasn't originally going to take a film camera but the wife suggested it knowing I'd like a couple of negs to play with later on.
Camera will most likely be travelling in baggage as I will be carrying the dSLR (Pentax with 16-45, 50-200, flashgun and maybe a 180mm macro) and unless I can distribute bits between family members (who have their own junk) I'll be overweight with my carry-on. Camera body is a real old 645 1000s of no monetary value and I have a spare 80mm of minimal value so I'm not concerned from that point of view. As we're doing several road trips in cars where we want everything to fit in the boot (trunk) we're trying to limit our baggage to 2 cases and our carry-ons (which in my sons case means iPod, DS's and associated chargers!)
We're doing the Yosemite section out from SF, then flying to LV to pick up the RV. Would have liked to go over Tioga Pass but like the last time I tried that (1996) our timing is not suitable. One way drop off fees were a killer too so we decided on a loop out of LV. Hopefully those are likely temps... we don't want it too cold which we were thinking it would be!