Congratulations on your new additions
Don't feel bad! You have joined a really good forum and are doing research and asking questions which is great.
There are a number of bedding options and it really depends on what you find best and what suits the housing you have for your guinea pigs.
If you are using something disposable then try a layer of newspaper first, then your bedding so wood shavings, megazorb or eco pet bed
http://www.ecopet.co.uk/ or similar and then hay on top of this for warmth and them to burrow in. Remember they need hay to eat as well so try putting this in a rack off off the floor (stops them treading and peeing on it!).
As others have said, straw is a definite no no
As for fleece, I have never used this outside but I use it for my indoor piggies and love it - they have a C&C cage which has a liner in it. There are lots of posts on using fleece and liners (some members on here make liners if you aren't handy with a sewing machine).
HTH and enjoy your new piggies. Our children adore ours
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