Thanks for the info guys, and for those links to the trip report links, Bob. Both of those outings sound like total monsters! Winter's a different beast altogether, isn't it. Like I said in the original message, we're not aiming to reach Whitney's summit. Time in the mountains, rather than peak-bagging, is our goal. Although, perhaps a smaller, less distant peak like Thor Peak might be an option?.
I reckon our aim will be to camp at Lone Pine Lake for our first night and just assess the conditions from there. If the snow's good, we might head up towards Trail Crest with day-packs. If it's soft and sugary and deep and horrible, it'll be back down to the N. Fork and hopefully better/less snow up to LBSL. Do you reckon it's reasonable to aim for Lone Pine Lake in a day's travel from the portal road closure? Also, how easy are the lower sections of the Whitney Trail to navigate after dusk or pre-sunrise?