I think you could just announce that it’s a recon force and which ships would be passing through if it succeeds… maybe put the recon force into the territory for combat and the rest of the fleet could be put on the line between the territories until combat is resolved. If the recon force takes out the blockers in the first round of combat, the ships on the line could then pass through the territory or use their shore bombardment in the territory: but the recon force could not pass through with them and could not bombard with them (they would be out of position, expended munitions, etc.). If the recon force fails to take out the blockers, then the remaining ships may join the combat or they could stay in the previous zone and either way can’t pass through or bombard the shore. The recon force would then have to continue to engage in regular combat or retreat.