The original idea of the caravels and explorers was to help you explore the world. Now, since we've agreed to giveg each of you full map knowledge, the need for these units is a bit diminished. However, even if caravels are out of date, they would allow you to move units to other's islands to either keep track of what is going on or to cause mischief.
I would be reluctant to give warships or transports. If someone decides that war is the way to win, they should have to sacrifice spaceship building to build up an army/navy. If everyone starts with warships, the "penalty" for going "war mode" would be diminished.
But, this is your game. I'm just the map maker.