The trick for us was to plan an all-nighter with our 12-year-old. We rented a bunch of movies, or watched some we owned, and watched till we dropped. But from the start we said this wasn't going to be a regular thing. Our son was thrilled. We all fell asleep around 4 or 5AM...and lost much of the next day to sleep. Lesson learned...you still need sleep in there somewhere.
Natural consequences help a lot, especially when they are pushing up against Mom's bed-time rules. It probably feels very "mature" to stay up late. But are they bears the next day? Do they have chores or help out around the house or have any commitments the next morning? If so, hold to them. Let them experience the tiredness and then talk about it another time when they have more energy (not when they're tired and grumpy!)
Also, I would try a few different things. First, I would PLAN an all-nighter movie night and see how long they last. The parameter (arranged beforehand) could be, if they do an all-nighter, they need to respect the ones who want to go to bed and be quiet enough for them to sleep. If not, all bets are off, and no all-nighters. If they succeed in letting the sleepers sleep and behaving within the bounds you set beforehand, then another one could be scheduled for later in the summer.
Once the thrill of being allowed to stay up all night is experienced, they (hopefully) will discover that they feel awful the next day--tired, grumpy, harder to think or make decisions, acid stomach, etc. They may actually discover that sleep is a wonderful thing.
Second, I might give them a predetermined date (the end of this week or next week) to say they can stay up till some predetermined time (midnight or whatever is decided). But then after that, it's back to regular bedtimes. At the end of that "free period" for bedtimes, you can all talk about what you liked the most and least about that time--you included. What amounts of sleep worked best for each kid? What didn't work? They'll all have different needs.
Lastly, I would make sure they still follow through on their commitments around the house or elsewhere. In fact, if they have trouble with going to bed once you've returned to more sane bedtimes, I would add a chore (remove a privilege) for every time they stay up beyond a pre-determined time. Talk about it beforehand so they know what is expected. Include them in the discussion of what time should be the bedtime. If they don't like the added chores, they have a choice of going to bed at the appropriate time. It's their choice. (Meanwhile, your house might get some needed projects and/or cleaning done!)
My husband and I are both late-night people. It's rare that we are in bed before 11 or 12 at night. My husband gets up around 5-5:30 every day for work and then catches up on the weekends. I need more sleep than that. For a while I was getting 10-11 hours a night (I'm a stay-at-home mom when I'm not freelancing), but usually 7-8 hours work for me.
Each person is different, but it might be worth it to read up on "sleep hygiene". Just Google it and you'll have plenty of reading. And then talk with your kids about it.
My doctor said that an ideal amount of sleep for adults is 5 REMs, around 1-1/2 hours per REM, totaling about 7-1/2 hours each night. Some people's sleep cycles are shorter than 1-1/2 hours, others are longer. But she said the 5 REMs was the most refreshing for people--not too much, not too little. For our son, he survives best on 9-10 hours per night. During the summers, it's more like 10-11 hours.
If you do an overnighter, do it when you have time to join them. Make it a fun adventure that you plan ahead. Let the excitement build, knowing that you'll all need some sleep and patience the next day. It might be a challenge with five kids, but it might be a fun adventure they remember, knowing that they aren't always required to go to bed at that "boring" time. Loosen the leash a little, but don't give them the leash! With a little planning and engaging them in the discussion, you can reestablish boundaries that work for all of you. Clarifying expectations beforehand goes a long way in helping define boundaries and rules, especially if your children are part of the discussion.
Have fun and good luck!