Hi and welcome. Wood chip can be too harsh on their feet and some wood can absorb guinea pigs natural oils from their feet. There are wood substitute on the market that go through process to remove dust and make it less sharp - auboise is one of those.
Apple branches are good for pigs however I am never happy giving them to baby guinea pigs...
There is a lot of information available on bedding, environment, food etc that will help you providing the best care possible for your new fur-babies.