I'm scrambling to catch up here...just fantastic! I won't bother to spend to much time gushing because others have taken care of that already (I'll do my gushing privately, lol).
Any estimates on the year? Anne, you're right. On one hand judging from Tatiana and Olga they look like they could be 1912 or 1913, but Anastasia (unfortunately the least clear of the sisters in these photos) and to a lesser extent Marie both look older. Almost like it could be as late as 1915 or '16.