Re: Would it bother you if..
Wanting to be there and making the effort to do it - Great! However, not being considerate to ask when it will be a good time to visit and stay, is a big no-no in my book.
Maybe you (or DH) could let him know that the actual day/week of her birthday is not good and to visit the week before or after. Thankfully he gives notice so there is time to adjust things.