Nope, sounds wonderful to me that he wants to spend all this time with him. But I do find it sad he is giving one child special treatment and not the other. I would approach it from that angle. He needs to take both boys out...
As far as you feeling his competing for special father-son bonding, just learn to tell grandpa no on certain things.
"We are busy that day" or "His dad is taking him fishing that weekend, but you can take the boys next weekend."
Of course, if dad isn't spending the quality time with his kids, that's one thing he needs to change. Grandpa can't do all the firsts if his dad isn't making the time to do it himself. If dad is spending time with the kids, then just let grandpa have time later, tell gramps the kids need a break to study or have another activity planned, then tell him what a good day would be.
Really though, don't put so much stock in those "firsts" what really matters are the subsequent activities that follow and that is what lasts.