My previous border was super happy as a family companion with lots on and off leash walks and lots of mental stimulation. My current border cross is just the same. I am surrounded by border owners who have very happy well adjusted dogs that do not herd.@Sunflower_, it depends on the dog, some BC's will drive you nuts, my neighbors have one and I promise you Milo does not have an off stitch. His "job" is too play ball and he will do that nonstop to the point where he cannot walk the next day. My five are perfectly happy to lounge around the yard all day and do nothing. Admittedly they are all older now, the youngest one is eight and they spend their younger years on a farm with lots of space to run and play.
But most of all, the op had indicated that she is willing to do what it takes to keep a BC mentally and physically occupied. And that is the most important trait and dog owner can have.
That being said, I would be very careful of bringing any breeding breed into a family with smaller kids, I know mine see kids as sheep without wool - to te herded into a corner and made so stand still, and they will not hesitate to use teeth to achieve that goal. Something most kids don't appreciate.