I used to worry about that with toilet paper too but I don't any more
Been using it for years with no issues - it probably has less chemical processes than Carefresh which is wood pulp.
There are other beddings you can get in bulk. Zooplus sell hemp bedding in large bales if that appeals. I was allergic to it so used Fitch. I really like Fitch. The appearance varies sometimes. Some times it's very white, other times more an off white - I asked them about it once and they said it depends what they've been recycling. Usually it's white and reasonably soft.
Whatever you go for it can save a lot of money buying it in bulk and you can be generous with the substrate as well.
If you do go for that house, then maybe paint the inside with Plastikote. Only takes about 10 minutes, although two coats is best - I do the second coat the next day although some people find it dry within a few hours. Next day works best for me. Just means it'll last longer.
Yes childrens play sand is fine.
This is the hemp bedding
100 litres for £19.99
https://www.zooplus.co.uk/shop/small...ll_pets/182990
Rat rations also sell some beddings in bulk. The egg box carton one has been popular on here recently (Softacard). Out of stock though at the moment. About 15kg bale.
https://ratrations.co.uk/substrates-...rays/softacard
They also sell Megazorb which some people like. I haven't tried it because heard it could be dusty.
The other thing with a large cage is to have plenty of floor toys to fill the area and make it interesting - different levels and textures. The large cork tunnels are good for that