I like the sound of World Bicycle Relief. I'll look into them.
I am not a big fan of rail trails myself. I tend to be more supportive of riding on the roads. Rail trails tend to give bike haters and excuse to try to keep bikes off the roads. I am not totally against them and do think they are a great place for families especially with young kids, but building them isn't high on my list of things to donate to. I'd rather support someone who lobbied for laws that supported cyclists on the public roads.
Local co-ops sound great. My concern with them is they tend to come and go here. I'd give to one today, in fact I have some pretty nice bikes I plan to donate next week that would quickly sell on FB marketplace, but including a co-op in long term planning. I'd wonder about them being around when the time comes. I know one that was here a few years ago went bye bye recently.
Despite my philosophy not totally aligning with the ACA they will no doubt get some of my donor fund dollars. There are other outdoor and environmental causes, that aren't cycling related so I am not mentioning them here.