Going on a cruise, need to rent a lens, but wait! There's more

So I'm taking my 5D, 17-40L, and 50mm 1.4. I want to rent another lens to take with me. I need a longer focal length because I'm going to propose to my girlfriend and have my brother hiding taking photos. I was thinking 135L because it's $47 with insurance for a week, and it should be long enough. Wanted to get some other opinions though. I'll be renting from here: http://www.photorental​source.com/ as I can go pick the lens up in person. Thanks for the help.

70-200, more versatile.

I may grab the 70-200 2.8 Sigma lens then.

If you're going to have great lighting the Canon 28-300 USM L Series lens is great! If you're not sure on the lighting then the Canon 70-200 2.8 is a good choice.