The difference between me and my girlfriend is 5 or 6 inches. It's not that far off from you and yours.
Just give him an enthusiastic little jump if you can't quite reach. Like an attack kiss. It's kinda cute. But there's nothing stopping you from just walking up to him, face to face, putting your arms/hands on the back of his head, pulling his head down to you and giving him a nice sensual kiss. Sooner or later he'll get the idea. Just do whatever you want. This shouldn't be too hard.
That was about the height difference between my ex and I, he's like 6'1" and I'm 5'6", and we never had any problems kissing. You reach up on your toes if necessary and he bends down a little. I promise it's not as huge of a difference as it sounds, you'll be able to make it work easily. =]