My youngest sons (he will be 5 this year!) birthday is December 12th and mine is the 16th. My brother-in-law's is the 28th. While growing up I always felt slighted to some degree with the combo present. I think this is why I always make sure my son's birthday is completely seperate from Christmas. Also, by having him so close to mine I found that I completely forget about my birthday because I want him to have so much fun with his. As for my brother-in-law it varies year to year. This year it will be a combo gift card as he is currently stationed in Baghdad. Previous years were usually always seperate gifts.
Oh and the gift wrapping does matter.....it always matters! People wouldn't do Easter egg paper for someone with an April birthday so why do they do Christmas just because it is December.