Writing a letter

Hello guys! I have to answer to an email. I've already written the email so I'd like you to check it and tell me what should I change.

Part of the original email:
"Anyway, I was really writing to ask if you would like to stay a little bit longer when you come over. You've already got the wedding invitation - I can't believe my sister's getting married in a few months' time! I was thinking perhaps we could spend some time together before or after the wedding. Let me know what dates would be good for you. Also, my mum would like to know if you wouldn't mind sharing a room. We're going to be quite busy, what with the wedding and everything.

I know this is your first time to Britain, so please let me know in your email what kind of things you'd like to do when you're here. We're going to have a great time."

My response:
"Subject: Your invtation

Dear John,

Thank you for your email. I'm glad to hear that your sister is getting married and I'm really looking forward to the wedding. I'm sorry for being a little late, but I've got my hands full with studies for my final exams and I haven't had time to check my email.

Thank you so much for inviting me to stay a little bit longer. I'd love to spend some more time with you. I really need a break after this long school semester. I'm going to finish school on 15th July. Is it OK if I arrive on Monday 18th and leave on Friday 22nd? If these dates sound good, let me know and I'll book my plane tickets.

Now where was I? I nearly forgot, what kind of clothes should I bring to your sister's wedding? I've never been to a weeding abroad before. Also, my parents and I would like to buy a present for Jane. What do you suggest? I guess a camera is a good idea, so she can take pictures during their honeymoon.

Finally, you've asked me about what kind of things I'd like to do when I get there. I haven't though about this much, but I guess the first few days we'll be busy getting ready for the wedding. After that, though, there are one or two things I'd like to do. I heard that Madonna is going to held a concert there and I'd really like to go. I guess a day sightseeing in London would be great too! Other than that, I'll leave it up to you.

Anyway, I hope to hear from soon.

Take care,
Alex

PS By the way, could you please tell your mother that I don't have any preferences about the room? Whatever is easier for her will be alright.