I didn't want to wait for someone else to chime in as I could lose power at any moment & not get it back for who knows how long.
A sad thing indeed to have to post about. I have not yet had the experience of culling out any rabbits, however I have had to with my last group of chicks when I got them.
I did some searching & there is really no nice way to do it (for you) with out causing more potential pain on the rabbit.
With them being so little I personally would prob choose to dig their resting spot, place a flat rock or flat board at the bottom, find a large rock that has a flat side, put them in the hole with some of momma's fur then drop the large rock on them. It sounds horrible but I feel that it would be the quickest way w/ the least amount of any feeling on the kits part.
If you want to read the one that was most helpful, here it is
http://www.angelfire.com/wy/deb/euth.html
With my day old chicken, it had taken 24hr to get out of the egg - it was stuck & when it got itself free, it ended up making a little tear in it's stomach causing the intestines to start coming out. I was not able to to tie them off or get them back in due to the section & such. I ended up having to use the blunt force to the head method as I felt it was the best way for it's small size
It's never easy having to do this (It took me hours to muster up the emotional strength to have to take it's life) Just cuddle them up & know that you are helping them rest peaceful instead of suffering slowly.
Maybe some other people will chime in that have had to do this so they can share
You are a great person for putting your feelings aside to think about theirs first