Interesting idea, but I don't think the sail would be nearly enough to counteract the gravitational acceleration caused by getting near the target system, let alone losing enough speed to enter an orbit.

>> Each spacecraft would be the size of a DVD disc

Not much room for a light sail large enough to fully offset the power of the launch lasers.

In short: no. It'd need to slow down enough to counter-act years worth of a laser specifically making it go faster. Without a laser on the other end, really no shot.