In Florida, eucalyptus mulch is available to buy and quite a few tortoise keepers use it as substrate. I've hung eucalyptus branches in my aviary to keep bugs away. Manouria use pine needles for nest building, and I think redwood needles would be similar. So, in MY OPINION, neither of those trees would be harmful to your tortoises. I have about 6 very, very tall eucalyptus trees lining my property on the neighbor's side and other than the mess with falling leaves and twigs, not harmful at all to my tortoises.
No. We have three huge redwood trees in our yard. Charlie has lived with them for 15 years without a problem. We aren't good about cleaning up the needles either.
The only issues I have with both redwood, is that it's very hard to grow anything under them, and the root system gets very dense and stays close to the surface. If there is any plumbing or drainage, the roots will find its way in and can plug everything up quickly.
The eucalyptus is listed as toxic by tortoise table, but also by the Calif poison control. I normally am not too concerned about level 1 and 2 toxic plants by poison control, but this is listed as a level 3. Very high in oils and tannins and phenolics and terpenoids which , in mammals, leads to vomiting, diarrhea, etc. I personally would prefer not to have it in/over a tortoise enclosure. It is also well know for being very difficult to get anything to grow beneath it.