Remember that any XP 'gained' while the PC isn't in the party is purely illusory and won't be credited to you. Bearing this in mind, I take party member who have Stealth and Security so as to stealth past the first few droids without killing them, leaving them alive for my PC to kill.
But then, I'm obsessed with maximising XP
If you just want to progress through the game, simply pick your most powerful 2 characters. Bear in mind the droids on the yacht hiot quite hard, so you might want to pick someone with quite a few hit points, so they don't die in one hit!