Are you planning on playing airsoft right after the tattoo? Because thats going to hurt 10 times more. And could mess with the tattoo, that would be the worst news. Doing a cover-up on scarred tissue.
Tattooing is purposely scarring the tissue to leave the ink in. Getting shot, isn't going to really effect it. But, if skin came off, that was deep enough, it could come off. Even if it did, you'll either have to get it "re-inked" or fixed sooner or later down the road.
Of course, repeated abuse towards the area, like regular skin, will warp. But I doubt your going to sit there and take multiple direct shots.
Just cover it up after you get it. You should be fine. Since a tattoo is just a paint-pigment. Be more worried about the tattoo loosing color, or your skin stretching.
If worse does come to worse, be prepared to come back to the needle. Though, you'll might think twice.