In that situation, as a GM, I'd be more inclined to take a 10-man into the normal raid with people being slightly undergeared than to go for LFR. Save LFR for the end of the week and you won't be losing out on potential upgrades yet you'll still have the chance to get more guild members involved. Besides which, 10-man shouldn't be *too* inaccessible; this week I downed the first boss with a raid with gear in the mid-450 range, and while we're raiders with slightly more dedication than the masses, I wouldn't call us particularly hardcore.
Our original schedule was to start official raiding *next* Wednesday (not this coming one), with unofficial raids being permitted in the meantime. Some of the officers have been pushing to move that earlier, but I think I'm going to override them - the guild as a whole isn't ready, yet. They can certainly roll out a squad, but there's not a lot of leeway in there. Besides which we'd *kinda* like to get back to 25s if we have the people, and I'm worried folks will be reluctant to do that if there's a 10-man who's already stormed off doing everything they can in the meantime.