I do agree it is rude to ask feeding mothers to cover up HOWEVER I feel that most people who do get offended are generally the ones that 'pop it out extremely indiscreetly' and make a point of feeding. I totally agree (I am a mother, who has fed) and I find it uncomfortable when a women starts to feed especially at a dinner table or around strangers. Yes I understand it is not a sexual act, it is natural, it is the only way a child feeds (and all the rest) however in Australia breasts are considered taboo to be shown in public, and their is still a lot of uncomfortableness around them being exposed in the presence of strangers. Yes many women can do it discreetly, but some don't. If there are only 4 feeding mothers, I would be inclined to approach them all individually and tell them that you have arranged a room at the reception for their comfort. I would go down the lines off how difficult it is to get a newborn to feed when there is so much noise and activity going on around them, and also as a room to settle bubs and perhaps change nappies etc - just a little room for mums and bubs.
As for the church, I am actually surprised by how many people don't settle their children. I don't know whether people are just immune to all the noise their kids make, or they are just rude, maybe they think it is cute - but many people don't leave the ceremony when their kids are unsettled. Hopefully being such young babies, their cries aren't yet loud so it shouldn't be too much of an issue, however I would still get the priest to say something at the start. Maybe the priest could approach mothers (families) when entering the church and ask them to sit at the end of the pews for an easy exit should bubs become unsettled - people don't seem to get as upset when a priest asks them to do something, as opposed to someone they know. I would again get the priest to mention to along with turning off mobile phones.
Oh, and I'd add to be fairly blunt about the kids' noise being captured on the wedding video which would render it an unpleasant thing to watch in the future, so could they please ensure they move off the second their kid makes a noise.
Maybe just word it a bit nicer than I put it lol