Without being able to see the bloom, its almost impossible to tell the type of plant that is. Looks like some sort of day lily. Some of them are toxic, some aren't.
If it is pampas grass it's ok. Just be prepared to see if mowed over. They like to hide in it, I have never seen it being nibbled on by multiple species of tortoises I use it with. Should be good for go with it. One other thing to keep in mind with fountain, pampas, and elephant type grasses are, when they get big they can have a sharp side to them. So keep an eye out for any slicing or open wounds on the torts. Shouldn't be a problem with larger tortoises. But keep that in mind. They typically don't get sharp serrations on the plant stock until they're really big, so it may not be noticeable with smaller plants.