Hi Claire,
Don't panic! for a start you haven't reached your due date yet. It is true that once intervention starts then the chances of more intervention are higher, but having a sweep certainly doesn't necessarily mean that you're going to have a more complicated or longer birth. Your midwife may have picked up on the fact that you're impatient to meet your baby, and so have suggested a sweep to get things moving. Unless there are good medical grounds for having a sweep you don't have to have one if you're not comfortable with the idea, and if you're prepared to wait a bit longer for nature to take its course.
As Tracy says though, depending on the circumstances, if the doctors think that your baby has been in there too long then they might want to schedule you for induction if your baby is over a week late - it'll depend on the health authority. BUT, you can resist that to a degree too, and ask if they really think it's necessary. If you get the feeling that they're planning it for their own convenience then ask them to tel you why it's medically necessary / what the alternatives are.
Bear in mind that babies are only born on their due date 15% of the time. Also, your given due date is usually down to the vagaries of the pregnancy wheel, so may be quite a bit off.
If I were you I would call your midwife soon to discuss the sweep. Tell her that you have reservations about a sweep and would prefer, if possible, to have labour start naturally, if that's what you want. Don't be pushed onto anyone else's time schedule for their convenience, rather than for medical imperative.
As I say, she might be under the impression that timing is very important to you, if a fully natural birth is more important then it'd be good to discuss that with her. also discuss what it could mean in terms of induction if you go significantly past your due date.
HTH