Not changing the fleece for 8 days isn't ideal, but I think it's workable in a rare circumstance like this. But the poop in the cage will definitely need to be cleaned up. You can't really fully litter train guinea pigs. I wouldn't be surprised if you could at least reduce how much they poop outside of a designated area, though if you're just starting now I'm not sure even that could be pulled off. Realistically, guinea pigs won't ever poop in just one area because their metabolism is too fast. Cats can be litter trained, but bare in mind they'll only poop something like 10 times a day (I don't have a cat, but I did clean the litter for a friend's cat and that seems like a reasonable maximum from my experience). Maybe more than that, but it's nothing compared to a guinea pig. For one, their poops are smaller, and again, they have a much faster metabolism because smaller animals need a faster metabolism to maintain body temperature because of the cube-square law. They poop more on the order of 50-100 times per day. That's around once every 15-30 minutes, and it's just unreasonable to expect them to be going back to the same area that often, they frequently nap longer than that.
Probably one of the easiest ways to handle poop is to vacuum it with a handheld cordless vacuum, I've had good success with the Shark Pet Pro Plus. If the cage isn't already on a table, you could move it on to one so there's no bending down required. But even if you do that, hay can clog up the vacuum. The Shark is at least better than this than the other vacuum I tried, which would get clogged by the littlest thing, but you still have to empty it quite a few times. There is a button that opens the chamber for easy emptying, but if you pick up too much hay before emptying it, it will get stuck and will have to be pulled out somehow. I usually just sweep up the large piles of hay first and empty a few times and it's fine, but you still have to sweep or you'll be emptying constantly. You can also just try sweeping everything, but depending on the circumstance that can be even harder. Also a rubber brush is pretty much a must as hay will stick more to a regular dust brush and you will often just spread the hay around. Also, the guinea pigs may not like the loud noise. Mine weren't bothered by it even the first time I used it, I more had to keep them from trying to investigate it, but not every pig is like that.
If you have an area that is covered (perhaps by a second level), they will poop more there, so if you keep that further from where you put the hay, it'll at least reduce the amount hay gets in the way. But then you would have to move whatever is covering the area to access it while cleaning.
If that's not feasible, you'll have to find someone else who can handle the cleaning. 8 days worth of poop is an insane amount, that's just not workable to have the cage not cleaned for that long, it really should be at least once a day.