How long each day?
All dogs should get a daily walk, but it's important to be realistic about how long you can manage daily as some breeds are ok with an hour or less, while some need several hours.
We have a cocker spaniel, I wouldn't let him free range with our rabbits as if they ran he'd probably thinking chasing was fun (although he ignores them in their enclosure & is more interested in eating their poop). They have a large secure enclosure anyway as we get regular fox visits, but I personally avoided terriers and sight hounds as they have stronger prey drives for small furries.
Our dog is ok with an hour a day (I'm pregnant so not doing as much as usual) as long as there is plenty of mental stimulation, lots of sniffing, & he's fed from a kong or puzzle feeder rather than a bowl. He's part working, part show; a full working spaniel (like his mum) would need more exercise & stimulation.
They are fun dogs but v bitey puppies (all puppies bite, but gun dog breeds can be particularly mouthy). Think carefully about how you'd manage this with young children; they grow out of it but it can be quite full on especially when overtired. Easier if you can use baby gates / room dividers, harder if you have a v open-plan layout.
Also, they can be a bit prone to guarding - it's important not take things out of their mouths by force. It'll be easier to manage if kids are old enough to understand that toys/shoes/gloves etc need to be kept out of reach or risk being chewed!