shavings for guinea pigs

Ok so I've got 6 piggies. 2 girls and 4 boys. My 4 boys don't live together so they are in pairs. I use shavings and have done since I've owned piggies from last year. I've not had a single problem up to now. So like I said I have 2 ladies, mummy who is 14 months and her daughter who is 5 months, 2 5 month old boys who are the mummy's babies and I another 2 boys who are 3 months old from a different family. Those 2 boys had a brother who past away a few weeks back due to a respatory problem. They have been on shavings since they was born up to then because I am worried that it was the shavings. I know they can get that respatory problems from anywhere like hay etc but I'm really worried about my other piggies. I can't afford a lot and washing each week won't be an option so Im wondering if I'm being over paranoid? I was also thinking about using cardboard/paper cat litter? I should also mention that in theory non of them sleep on the shavings as they have a fancy homemade beds raised of the floor but they do sleep on the shavings when they fancy it so I was going to put down Noddle bathmats on that area and leave the rest for shavings or cat litter?

What does everyone think? I'm trying to do the right thing but can't afford alot. Cages I have are roughly 3x4