Building on the earlier suggestion, I actually had a similar dilemma for a destination gig last year. I tried making the Canon RF 24-105mm f/4L IS USM work because of the weight, but even with the stabilization, I ended up with more noise than I liked in those old buildings. Since you have a $2500 budget, you can definitely afford the Canon RF 24-70mm f/2.8L IS USM if you look for a refurb or used copy. Ngl, those savings could go toward extra Canon LP-E6NH Lithium-Ion Batteries or faster media. The 24-70 is heavy, but the f/2.8 is technically much more reliable for indoor ceremonies. It basically gives you that safety net when the light starts dropping... definitely worth considering for a high-stakes shoot where you cant control the environment.

Listen, if you're shooting a wedding, especially in Italy, that f/4 is a gamble you really dont want to take. I've spent years hauling gear through European venues and the lighting is basically always a nightmare. You're gonna find yourself in some 500-year-old church with tiny windows and the f/4 just wont cut it. In my experience, you need to grab the Canon RF 24-70mm f/2.8L IS USM. It fits your $2500 budget perfectly and its the industry standard for a reason. Tbh, the R5 sensor is amazing, but you still want that extra stop of light.

• That f/2.8 aperture is non-negotiable for subject separation during the ceremony.
• The R5 has incredible IBIS, but it wont stop motion blur when people are moving in a dark reception hall.
• You can always crop in with those 45 megapixels to get the 105mm reach, but you cant fake a wider aperture in post. Honestly, the weight is something you just gotta deal with for a professional gig. I've tried many different setups and the Canon RF 24-105mm f/4L IS USM is a fantastic general travel lens, but weddings are a different beast. Ngl, you'll regret the f/4 the second the sun goes down or you walk into a dim ballroom. Just pack one less pair of shoes and make room for the 2.8 glass... it's the right tool for the job.

Works great for me

Honestly, everyone is obsessing over the zooms but are you really going to survive a full day of wedding photography without a backup prime? I have had issues with heavy zooms failing in the heat, and unfortunately, the weight is not as good as expected when you are walking around Italian streets all day. Adding my two cents: before you commit that whole budget, are you bringing a second body? If not, you are really playing with fire. Personally, I would just get any solid prime from Sigma or Tamron if you want to save cash and keep your gear lighter. Their newer stuff is super reliable and sharp enough for the R5, plus it takes the pressure off your main zoom failing mid-ceremony. Why not just grab a fast prime for the dim shots and a cheaper, versatile zoom for the rest?

Look, I have shot more weddings across Europe than I care to count, and the weight issue is real but not the main problem. You are stressing about the glass, but have you thought about how you plan to light those receptions? I have found over the years that the lens choice matters less than your ability to kill the shadows in those cavernous Italian stone venues.

• How comfortable are you with your high ISO performance on the R5 when you have to crop in post?
• Are you planning to supplement your gear with a portable speedlight or are you strictly going to stick to natural light? Before you drop all your cash, just tell me if you prefer a clinical sharp look or something with more character for your portraits. That changes everything.