Guess Im nuts, I haven't had a big family party since my kid was prob 5 . He started wanting slumber parties and that is a drop and run kinda thing. His cousins are invited , and they come, but Mom and Dad ( his Aunt and Uncle) drop and run. My parents don't even step foot in the house, why would they with 12 screaming boys running around lol. I always have cake for the Grandparents if they are free the evening of DS's birthday , but I don't get my feelings out of joint if they can't make it . They always see him and they will see him with in a day or two. His Godmother will join us for dinner and cake too on day of , but same goes, if she can't make it she will see him very soon . His Godmother has a 5 year old dd, we adore her , but there is no need for her to attend an all boy birthday party . We don't go to her fancy princess parties , but always see her.
I just don't think its necessary to invite all the extended family , he wants to be with his friends and that is what the party is for.