I take mine outside on occasion when the weather permits. It took sally, my lop, a few times to actually enjoy herself. She spent most of her time in the carrier but after the third time she would come out and explore. My other bun Harley was excited from the get go. Binkying around running, jumping, mowing the lawn. I think it’s because Harley was from a reputable breeder and she would let the buns out in a huge run every day for a few hours to run and exercise in her garden so he was kinda used to it. And Sally was a pet store bun and I’m sure it was the first time she stepped foot on real ground lol but now they both really seem to enjoy themselves. Sally is just more aware of her surroundings and cautious but she binkies around.
I just always provide them something they can go hide in if they were to ever feel uncomfortable. And I don’t even bother taking them Out at certain times of the day when it’s most noisy. Like when children are all over the place walking home from school. Stuff like that. Get to know your surroundings and take them out when it’s most quiet
Also do NOT put them on any kind of harness. And sit out there with them at all times. And a bunny proof fence is a MUST. Do not let them out loose. But you don’t HAVE to take them outside to have healthy happy bunnies. I think it’s more for ourselves than our bunnies anyways :p