You have the best reason in the world for keeping theA5, it belonged to your grandfather. The gun is part of family, a link to the past, what did he hunt with it or was it used for clay shooting.
It will be much easier to show your kids this is the gun your great grandfather hunted with rather than telling them. Stories give no real connection to our past, but if one can touch/feel or use something from the past there is a bond there. KEEP IT as it is!!!!!