Agree with above that it would be best if you can ask a friend or your next door to check on them ideally once a day but even if you can leave them extra water and hay (pellets are nice but don't leave more than one day portion as they can eat too much at once and get a blockage. Not all rabbits are that greedy but some are so better not to risk, they can perfectly live without pellets just on hay and water for a few days, even for a week or longer)
In my own experience max they were left alone two years ago I was away for 4 and a half days and I wouldn't suggest leaving for so long alone but I was prepared very well and planned every little thing in advance and did a few trials while I was still home but everything was set like if I am away.
So I left two giant water bottles for each (each bottle 1100 ml), bottles were fixed firmly with extra wire so they can't move at all, for Fred I left less water since he doesn't drink much, just 70ml a day so I left 2 smaller bottles, but still two for each just in case ball gets stuck in one. Bernie drinks 200-300ml per day for instance so there was still lots of water left. Also I used boiled water just to stay on safe side.
I left loads of hay in hanging outside mangers, I also added some pellets inside of them so when they eat some hay pellets just falling with hay and they can have some, but as I said this wasn't necessary if they only had hay and water they will be completely fine.
I left one normal portion of pellets for everyone so first day without me they had full dinner and they had their vegs as well.
When I came back on day 5 they were all good, except of Bernie was very hungry. She normally eats tons of hay and I knew that and left really lots of hay for her but she ate it all, absolutely, there was no single piece of hay on her floor, even soiled hay was all picked up. So I felt a little bad for her but others were all happy.
Toilets were all good, of course I left them all clean and put grates on wood pellets to prevent digging, sometimes Bernie and Smokey get bored and would dig it all around so I just didn't want it too be messy. Fred would never dig his toilet, he only goes into one corner and when his spot is full he brings a piece of cardboard and covers that spot, or covers with a little hay.
So it was all success but I wouldn't suggest leaving for so long. If you are away for only 3 days and are able to prepare everything just like me, and maybe try this setup while you are still home and can see how it goes and make corrections, it could work. In fact, first day is just like a regular day they can have everything as usual so just two days they will be on hay and water.
Also I find that when they can't see me around they are more relaxed not seeking attention just cocooning. Since they are all trained now I can leave them for two days sometimes without any problem. But if you are going to be away for 3 days, as I said, first day will be as usual no need to worry about, I would ask if someone could check on them once (afternoon of the day 2), and you are back next day so that would be perfect.
Also I left dvd player on with their fav movie on repeat just used timer so it was switching off automatically for the night and on in the morning, just so they can hear nice music playing and people talking nicely like everything as normal. Sometimes I do this even if I am in town just not home for longer hours.
No free roaming during this time as well and make sure all doors are secured, I put a carabiner clip to fix them, one of my rabbits manages to open the door she is very smart girl her name is Arnie (yes when she was born I thought she was a boy and named her after Harry Tasker since she was born with tuxedo markings) she's an incredibly smart girl, she just likes opening her door all the time, she just opens it and says hello it's me your fav bun just in case you were missing me ☺
