CMM
It all depends on what you want to get out of it. You mentioned the word "holiday"... for me, fishing solidly (and I include the time you spend asleep in your bivvy) for 72 hours isn't actually a holiday... so maybe have a think about whether or not you want a night in a local pub as part of the trip? If you were to do this, will your gear be secure overnight?
If you don't want to go down the bivvy route, there's plenty of fisheries that offer on-site accommodation which can make your three day trip a whole lot more luxurious - you didn't mention if you'd actually chosen a venue or not?
Also, how many of you are going - and what's everyone else's expectations? If it's simply a case of four or five of you going for a three day session, then I don't really think you need to take anything different from a 24 hour session - because if there's that many of you, you can always take it in turns to go off and get re-supplied (i'm thinking mostly beer, food and bait). I do a fair bit of camping too and I'm starting to think that taking a load of food with you is not the best way to approach it - take enough for the first 24 hours then hit the local shops. You might want to take some more clothes with you (unless you're happy to put up with being minging!)
I organise a trip twice a year for myself and three or four angling friends, usually for 2 or 3 nights. To begin with, the fishery was always the most important part in the equation - however, having done lots of different trips now I would say the most important thing is making sure we all have a good time. So we'll stay in a pub or b&B and have a couple of really good nights out (the fishing tends to suffer as a result, but there you go...)
One piece of advice I would give you is to check out bulk bait supplies. Again, assuming there's four or five of you going you can get some good bulk deals on things like pellets which can make a real difference over 3 days. I've used AA Baits in the past (google em) bbut there's plenty of others.
