Carys,
I don't know how accustomed to owl post your grandparents are, but this is too short notice to use muggle post. I know you haven't got tickets to the Quidditch World Cup yet, and I suddenly have a spare one, if you'd like it? I mean, it was Victoire's but something came up at her work so she can't come. You don't have to come if you can't make it, but it would be nice to have you there!
The thing is, our tickets are the kind where we have to turn up quite a long way in advance. So we'll have to pick you up early tomorrow ready for our portkey at 2pm. We won't turn up in your fireplace or anything, Dad can apparate us both fine. So we'll be knocking on your door at about 10am, if you remind me of your address?
We have pretty much everything sorted, all I need is a response from you ASAP! Gallileo Figaro (my owl) will stick around for a while. I've told him to hurry you but without pecking too much, sorry!
Louis.
ps. You'll have to share a tent with Dominique. She doesn't snore. Too much.