Informal v. formal letters

Dear Georgie and Colum,
(First of all, let me say) thanks for your invitation/got your invite today,
I'd love to come and celebrate the big day with you / It'll be nice to be with you at/on this special occasion.
I have some questions for you, if you don't mind /  But my question is:
Can I bring Richard with me? / Will it be a problem, if Richard comes with me? / Is it okay to bring Richard with me?
Also, I don't understand if we're invited to the official wedding ceremony or just the reception / Also it is not clear, id we're invited.. 
At last, I'd like to know if it's possible to park at the restaurant../We're going by car, which reminds me - Is there any parking at the restaurant?
Thank you for your invitation
If you need some help, feel free to call us
I'm looking forward to hearing from you soon
Thanks in advance for your response
Lots of love, / Good luck!

Dear Sir/Madam,
I am writing in response to your advertisement which I have seen in a magazine../to your brochure.
I would like to ask some questions regarding/about the language school:
Could you clarify what kind of trips are included / what is the destination of the trips?
I would also like to know how many students there are in one group, as I prefer smaller groups..I would like to know exactly how small the groups are.
Is there also a chance to stay with a host family?
Lastly,  I would like to know the exact number of school hours a day.
I would appreciate if you would let me know/reply me as soon as possible. Thank you in advance for helping me to decide for your school.
Looking forward to hearing from you,
All the  best,/With kind regards/Best regards,
XXXX