8 lamps, assuming 55 watts, will pull about 500 watts... 40 amps. you'll want 2 30 amp relays and fusing to match. Fusing needs to be very close to the power source, be it the battery or the main power bus to the fuse box. 20 amps per relay isn't bad... I'd run 14 or 12 GA wire to each fuse/relay, and up to the lights.
This is not the sort of wiring that will stress a WK. their wiring woes are more associated with dirt and bad grounds after a bunch of wheeling, or minor nuisance problems like you get with any modern car. 40 amps is no more than a pair of heated seats, and any off-idle rpm should allow adequate juice. if worried, you could add a voltmeter to keep an eye on things.
One suggestion... maybe use more than one sw to drive separate relays-- so you can turn off what you don't need. you might like having that control, say if loading/unloading/camp set-up with engine off. or just not blinding folks behind you on a trail.