Well, yes, introducing slowly always is a good idea, and in my opinion the more diverse their diet is the better. Since mine grow up that way I can't tell if they need time to rediscover their instincts, or at least to get over the exitement of all thisn new, good stuff. I would start with grass and known safe weeds and then just gradually start to offer everthing except stuff you know is really toxic.
I totally stopped to care about those toxic lists on the internet. If they eat it, it's safe for them, no matter on how many lists it is, very little can harm a rabbit, and here that's mostly decorative plants. I can't controll it anyway since I let them out to forage.
There might be plants in your location that are really toxic, here there isn't anything they can't stomach or simply avoid, there could be hamlock but since there are farmers feeding cows here it's eridicated anywhere close to the meadows.