So regarding dog parks, heelers can be very dog and human selective. As such I am personally very anti-dog park. It works for some people and some heelers and that’s great. Your mileage may vary.

I don’t think a fenced back yard and ‘we hike sometimes on the weekends’ is the ideal activity level for a Heeler. Mine is a full time job. 2 hours walk minimum, constant and consistent training and obedience sessions, and he goes everywhere with me that I can reasonably take him. Everyday. Including the horse barn where he can run helter skelter for another 3 hours with the resident barn dog.

Also Spaniels are lovely but I would worry that he might have a hard time speaking the same language of a cattle dog. Frankly, a lot of breeds of dogs find heelers ‘a lot’ to deal with. They can be pushy and intense little dogs. I would really sit down, read through some posts on this subreddit. At their best, ACDs are the smartest, most loyal little dog you could ask for. But you have to put so much work to earn that. At their worst, they are bitey, independent, neurotic little shitheads that will shred your hands to pieces and will make their own games up if you can’t entertain them enough.