In the film, he makes that arrangement in order to bring Michael back safely. It seems unlikely that he would stake risk his son's life on a bit of cheap wordplay. The other families surely wouldn't respect the truce in that instance anyway.
He also swears that he won't be the one to break it "on the blood of his grandchildren". Shortly after we see him plotting with Michael against the other Families (partly because they know Barzini has a mole in theirs), and at the end Michael has all the other heads assassinated...and come the third movie, Vito's grandaughter by Michael is killed by a bullet meant for his son.
The death of Aldo Trapani at the beginning of the second Godfather game made more sense when I started looking into the first game. Basically, The Godfather II introduced "kill conditions" to allow the player to put a rival made man out of action for good by using a certain execution style. Aldo dies after being shot by a sniper, so he too must have had it as a kill condition, but because sniper rifles aren't in the first game, no one could touch him.
When I was playing The Godfather game, I wanted the Mob Wars to be fully playable, with running battles in the streets. Thus, I was disappointed when they boiled down to either taking out an enemy business or simply running to a FBI agent and paying some dues, with no bunches of gangsters popping out of the woodwork to rumble with. Some more playtime and deaths later, I came to a realisation: With the game's near-Nintendo Hardness because of its pseudorealistic damage model, having to fend out randomly popping out mobsters maybe realistic but definitely more frustrating than fun. Since the game may already try one's patience normally... -- User:Gentlemens Dame 883