I have accepted that I will make mistakes this year!! Great advice to yourself! You might avoid giving yourself a breakdown. I could not get one of the treasure hunts to load either, probably the one I would have use with your class too. and I have mixed feelings about going out first or starting at desks and books, no strong feeling either way. But I would look at how many days you have for "proper" lessons" in the first week. If you have 3, then I would probably do 2 at desks and then one outside, the order being up to you.