OK, I know some people will disagree with me on this, and all opinions are my own, based on my personal (limited) expereince.
Guinea pigs can be fragile creatures, and sometimes bad things happen.
When Ruby got sick recently I was shocked at how she was eating veggies at 8am and by 5pm we had to rush her to the emergency vet - she barley made it through the operation, and it took her over 6 weeks to recover.
This is an extreme example, but guinea pigs can and do go downhill rapidly when there is a problem (bloat, bladder stones, etc).
But I do also leave my guinea pigs alone (rarely) for up to 36 hours.
When you say you will be away for 2 days, do you mean 2 days and 2 nights?
How many hours (roughly)?
I think it is ok to leave piggies for 2 full days and one night, but in all honesty I would be reluctant to leave them for longer.
When we do leave ours overnight I always make sure they have an extra water bottle (in case one leaks, so they have a back up) and 2 bowls of pellets.
I tend to feed them their normal amount of fresh food on the morning that I leave, and make sure they hay trays and hay bags are stuffed full.
If I need to be away for 2 nights I as a neighbor to pop in and fill up water bottles and pellet bowls.
Longer than 2 nights and I pay a proffesional pet sitter to do things like clean and refil hay trays, sweep their cages, etc.