I'm 46 and have been riding for 27 years and consider myself a experienced all mtn rider, I've done the Heli and Cat trips and would do the Cat trip experience a hundred times over, before doing another over priced Heli trip, dollar for dollar you can not beat cat trips, you'll get two/three times as many runs, cheaper and a better vibe. Maybe split your trip up and do a heli trip for two days, take a days rest , then do a two/three day cat trip ?
As far as conditioning, B.C. powder especially with the wrong board in 2 feet of fresh, will kick your a$$ (compared to running groomers all day). I dont know either of the boards you're riding, but I would go with the longer one, just because of your lack of true powder riding. I'm 6'1" 200lbs and ride a Fish 160 as my powder board and a 161 Malolo as my all mtn board, both boards are insane in powder.
Bring an extra set (or 2) of goggles, not only for different lighting, but also if (when) you wipeout and your goggles are filled with powpow, you can grab another set.
I remember the first backcountry cat trip we went on and being worried about the threat of avi's, but once your there they really make you feel safe, just make to pay attention to quick avi training they'll give you, one thing that always sticks in my head is, if someone is caught in a slide, dont freak out and dont start frantically digging for your transceiver, just keep an eye on the person, the speed of the slide and when everything stops look to see if an arm, leg, ski/board is sticking out, then you wont even have to use the transceiver and waste time. It's once you make your first turns, you forget all about it, not to mention the guides know where the safest conditions are on the mtn.
If moneys not an issue, do look into some of the other B.C. operations Island Lake Lodge, Baldface, Redcats etc
But most of all enjoy your trip, it will be one of those lifetime memories.