My doctor recommended atleast 30 mins of excerising so i usually take my dogs out for a stroll and will end up walking for a hour i feel great after!
The more active you are during pregnacy the better your labor will go as your body is still in shape. Just don't over do it and if you ever wonder if an activity is safe ask your doctor before doing it.
Yes its great just dont over do yourself other than that feel free to walk as much as you please