[Will]

Well, since both are exploring, it is only a matter of time before one or the other stumbles upon their counterpart's solar system. So, best way to handle it that I can think of is broadcast information about the meeting, and just keep exploring. That's what the ship was doing in the first place. It isn't likely that an exploring ship will continue heading out radially from its starting point, so there isn't a risk of the other ship heading in the exact opposite direction to reach the solar system, and if they follow, they'll just be exploring the same places. Hopefully the lack of precise information on the home location of either would allow enough time for more in depth communication to occur to get a better feeling for motives, peaceful or otherwise, and time to prepare.