I think a great way to make your best friend from childhood of 29 years feel important on the day is to do the following:
Don't mention your thinking of setting a date until after your fabulous Hen party. Even then don't tell her just post photos on Facebook with descriptions of your amazing party!
Don't mention the date of your wedding to her until 4pm the day before. Then don't bother to call her just send a text with a simple message "Are you doing anything tomorrow? I'm getting married, you can come if you want". Then when she asks who is invited simply tell her it's just her and DS (don't under any circumstances invite her DH even though you was chief bridesmaid at their wedding and they paid for everything for you so you'd def be able to be part of their big day).
Just give the very basic details of the day ie it's at xxx at xpm (no further info necessary -don't make it easy as it won't be as much fun!)
Don't say thank you for the cards or presents they rushed out to buy you at silly o'clock (mind you the wedding was only in May so maybe there's time yet......).
When they eventually arrive and DS needs a nappy change after 3-4 hours in the car make sure the photographer stops them for 'arrival guest photos' just to ensure they are stressed enough!
At the meal make sure they are seated with people they don't know right at the back so they feel unimportant and cannot hear the speeches.
When they say goodbye to you at the end of the day after not having been spoken to at all just simply say "OK, bye". Don't what ever you do make them feel appreciated for dropping their plans, travelling a 8 hour round trip at very short notice with a young child and leaving dh at home, that would just spoil it!
Lastly don't contact them again unless it's via Facebook to ask for a copy of the photos they took!!
Bitter, me? Damn right I am!!