In terms of missing the introductions with your teachers, I would say it isn't ideal - you will turn up a week in, and they won't know who you are (assuming you're going to have different teachers). When I started 6th Form, those who didn't turn up for the whole of the first week were assumed to have dropped the class. You might be best sending in a note saying that you won't be there if you know who to contact, so that they know you are still in the class.
As far as course content, we did cover actual material, but one week of material shouldn't be too difficult to catch up with. It will be an introduction to the material, so you should be fine on that account. I attended the first four days of Year 12 before missing the next 6 weeks through illness. I was sent work by some teachers, not by others, and was caught up quickly enough. It shouldn't put you at a major disadvantage, just make sure to get hold of the work you missed - or at least find out what they covered so you can look over it yourself.