We could solve this problem by simply asking people for money to be given to us personally, and then making a large donation from that money, but right or wrong this feels disingenuous to me

I'm not sure this would be disingenuous. When we give someone money as a gift we typically don't expect any real future control over how they spend it; elsewise they would have given you specific objects or gift cards.

We could solve this problem by simply asking people for money to be given to us personally, and then making a large donation from that money, but right or wrong this feels disingenuous to me

I did both: we asked people to donate to recommended charities (only people who couldn't come did it) or to give us the money and we would donate it ourselves (my ex-wife's family was pretty generous with this).

The pro of asking them to donate directly is that you can elicit more engagement - if just one of your guests likes the idea and decide to copy afterwards, you already have a higher impact. If you want to do this, perhaps you could have an online campaign - like a crowdsourcing campaign. In Brazil, we often use doesuafesta to do it for birthdays - people can see others are donating, they can donate even if they can't attend, etc.

One thing to keep in mind: for most people the point of a gift is not to transfer an economic resource to you but to express something about the relationship they have with you (and they're willing for this expression to cost something; and, generally, we're willing as a society for this expression to come with economic inefficiencies: often, the giver chooses a gift (though less so at weddings) and the giver has much less information about the preferences of the receiver than the receiver). 

I think gift-giving is a psychologically tricky issue. I also think one shouldn't downplay the symbolic value in gifts -- rather, one should see the economic costs of a gift as a necessary cost for creating the symbolic value (rather than primarily as a cost for making a new coffee machine stand in the receiver's kitchen).

I just say this because often, donations to charity aren't a full substitute for a gift to the receiver: they don't fully create the same symbolic meaning. (I'd actually love to see a more general discussion of this: many EAs create fundraisers for their birthdays and I, personally, think such fundraisers partly miss the point of gift-giving)

 

One approach could be to have a small registry of meaningful, practical items you and your partner truly need, alongside the option for guests to donate to your chosen charity. This way, you provide choices for your guests, and those who prefer traditional gifts can still do so, while others who align with your charitable goals can contribute accordingly.
Weddings can indeed involve complex gift dynamics, but it's important to find a balance that reflects your values and respects your guests' preferences.
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One approach could be to have a small registry of meaningful, practical items you and your partner truly need, alongside the option for guests to donate to your chosen charity. This way, you provide choices for your guests, and those who prefer traditional gifts can still do so, while others who align with your charitable goals can contribute accordingly.

I did something like this for my wedding. Aside: it was to a global health charity that let us show a tangible impact, not a charity that was rated for effectiveness. I didn't know as much about EA at the time.

People did give generously. I suspect they might have given less than they would have spent on gifts, but I can't be sure, as we didn't have a traditional wedding either. I also do suspect that "many guests will likely give less to a charity than they would to [you] personally" but I'm not sure why that is. On one hand it seems strange to me; do you have any theories?

I didn't get any negative responses to my face, and some positive ones, although I got some vague impressions from family that some people might have been like "this is weird and pretentious" (but I'm not sure).

One reason to do this rather than asking for cash and donating it: it ties your own hands, if that's an issue. It can be hard to commit yourself to donating/hard to actually write those checks to the charity. (But that's not an issue for everyone).

I don't have plans to get married soon but I have thought a bit about whether there could be a way to substitute some gift for the equivalent amount of time from the person. I then can ask the person to read an article or watch a short video or similar as the gift to me.

So, for example, my friends would probably spend something like £40 on a gift for me if I were getting married now. I imagine that they value their time pretty low so I could maybe get between 1-4 hours of their time instead. I can think of quite a lot of content that they could read/watch in that time that I think would be great e.g. a few chapters of DGB/the precipice.

Maybe just making it into a nice web app would be enough to put it inside their Overton window? Probably not.