Wild rabbits are extremely difficult to rescue at that age. We faced the same decision last year when one of our dogs killed the mother rabbit. Among other things, the mother rabbit stimulates her young to urinate by licking their genitals, and this goes on for a couple weeks at a minimum. A human would have to simulate the same thing with wet cotton balls or something similar, or the babies die of uremic poisoning, or some such thing. It seems cruel, but nature has a way of dealing with these events. There isn't much you can do.