Well, I can't assure you about the ski and ride shool instructors this year, but when I was there (2011-2012 season), they received very good feedback from the beginners who were taking lessons.
I think some people just switch to skis because the learning curve is faster than on a snowboard. But although you might spend about 1-3 days until it "clicks", once you've got the hang of the board, the sky is the limit. I mean, the summit
People usually say that learning to ski takes less time and effort than learning snowboarding. Both are just amazingly fun, and the taste for one or the other is personal. I particularly love to ride, although sometimes I put on the hard boots to follow some friends. So, what really matters is having fun, and commitment. If one wants and has decided to learn snowboarding, it can take 1 hour or 1 month; it will be learned. The fun is what really matters.
Back to the resort talking, Granby Ranch for sure has more forgiving runs than Winter Park. WP greens are equivalent to GR blues, what makes GR greens a piece of cake, just so you can have an idea. Still, the runs are fun and long enough. That and also counting less people. WP is bigger and has more people, thus longer lines depending on the dates.
Besides that, don't worry about ages, I worked in rentals, and there was this gentleman who was in GR for a week, snowboaridng everyday, 10am to 3pm, smiling when picking his board in the morning and when returning it after the session. He was 70.
So yes, with my own experience, you and your group will for sure be very well served in GR. Can't give any info regarding WP snowboard instructors. All I can say is that GR usually has a great team of instructors, what sums to the very friendly slopes, which is an important point. And I think that what makes the real difference at the end is the person and his or her commitment to the learni g process.
I know that my advice shifts quite a bit to GR's side, but I am being honest, as a person who learned to snowboard in GR taking 1 or maybe 2 lessons (at all) on the free time and working myself solo on the mountain until the skills built up.
Sorry for the huge post lol :sly: