My iris plants are very old and now have very large holes in the leaves. Should I get rid of them?

Looks like possibly slug/snail damage.

Should I put something like Sluggo on them? What about all the ruined leaves. Should I cut them off?

I'd leave the leaves. They are still making food for next year's bloom buds. Just sprinkle the slug bait on the ground around them.

Yes, I would put some wild-life safe slug bait around the base of the plants. I would leave the damaged leaves alone - they are unsightly, but they are still photosynthesizing and feeding the rhizomes. At the end of the season, you can trim back the ugly leaves. The rhizomes should be ok.

Thank you all for your wonderful help on my iris problem.

If the plants are "old" they probably should be dug and divided later this summer.