The All Popular Travel Question

I'm taking a trip (honeymoon) to Croatia in October for two weeks. Will be flying into the south side of the country and meandering our way up into Slovania to the base of the alps. I planning on taking my Canon 6D and my 24-105 f4. I plan on a lot of landscape, city scape, and indoor photography. I'm worried about going to places that are indoors and low light. My 24-105 might not be able to handle dim lighting. I know with the 6D I can boost the iso, but I wouldn't mind having a backup lens to take that I can open up. I'm wanting to travel as light as possible. I'll be carrying a backpacking pack with all my clothing, and then a daypack for my camera gear. I've been considering renting a 50mm to take, but am not sure it is wide enough for the trip. I'm thinking there will be churches, museums, wineries, restaurants, etc that I will be in. Anyone have any better suggestions, pros, cons, experiences?

Sigma or Canon 35/1.4? Or the Canon 35/2 IS. I have found 35mm on FF to be a great nighttime/walkaround prime focal length.

Also, congratulations!

Hey, congrats on the wedding!!! Regarding the high ISO performance, it is really impressive what you can do with the high ISO performance of the latest bodies. I just started going through a recent indoor family function and my shots are ISO 2000-3200 with the 24-105 @ f/4. No flash....but that said, I think one of Canon's recently released primes is perfect for what you are talking about. They are small, light, f/2-2.8 and have 4-stop IS. So, I'd seriously consider buying or renting either the 24 f/2.8 IS, 28 mm f/2.8 IS or the 35 f/2.0 IS. For the f/2.8 lenses, you are getting an extra stop of natural light and an extra stop of IS (24-105 has 3 stop IS). For the 35 f/2 you are getting 2 extra stops of natural light and 1 extra stop of IS. Another pro for the 24 mm f/2.8 IS, the 24-105 f/4 has a lot of distortion at 24 mm. It would be nice to have the equivalent of 4x lower light ability and fix the distortion issue. That said, I may be most tempted by the 35 mm for the extra stop of light and slightly more narrow focal length. But any of the three would likely work well.

Trade your 24-105 in for a new, version II 24-70mm f/2.8L and a 10-22mm wide angle.

I don´t believe the 10-22 will not work on the 6D.
I would go with Neuro´s advice and choose the 35mm f1.4 (both the Canon and Sigma produces great results). An alternative is a light travel tripod, like the Gitzo GK1580TQR5. It is extremely light and compact and it is remarkably stable considering how small and delicate it is. Downside is that it, ball head included, is about the same price as the Sigma 35.

Although you only gain one stop, you could also get the 40mm pancake. It's tiny, inexpensive, and pretty darn good. I used it for indoor pub shots on my 6D in Ireland, and it did a pretty good job. Sometimes, though, the ISO had to push to 12800. A 35mm prime, although larger and more expensive, would be better though if size/weight isn't your primary concern.

EF-S 10-22 is a no go on a 6D, so that suggestion is out.

Set your 24-105 to 35mm and see if you could work with that. If so, consider renting the Canon 35/1.4 - Roger at LensRentals says if you've ever asked the question "why would anyone want to shoot with primes when zooms are so much more convenient, this lens will answer it for you". Or, if you're brave and comfortable with manual focus, rent the Zeiss 35/1.4. It's MF with "AF assist" (the viewfinder light blinks when you get it right, or almost so). I've never used it, but having used other Zeiss lenses (now you've got me dreaming about the Zeiss 100 Macro....yummm) and Roger's commentary, I'm very anxious to try this one.