My friends have a cavoodle with two kids a similar age to yours and although he is a gorgeous boy, he is a lot of work! They take him for a 5km run most mornings. They need to be very firm with him as he doesn't like to be told what to do, and he still jumps on the kids at 2 years old. And he chews anything that's within reach, including kids' toys
Cavaliers do shed a fair bit but IMO they are a very good choice for a family dog.
Keep in mind that any dog that doesn't shed will need to be taken to the groomer around every 6 weeks. I have friends with purebred poodles who let them get shaggy and you couldn't tell them apart from a cavoodle sometimes.
No matter where you get your dog from I would find a breeder who will allocate pups based on their personality and their potential family's individual situation. Temperaments can vary within a litter and for a family with kids you don't want the most timid pup OR the most energetic pup.