To be honest I would wait until your youngest is 5 and starting nursery/school. Puppies and dogs can really tie you down, even if they don't have separation anxiety. You have to bare in mind they can't go into kids play areas at the park, so you'd always need one adult holding the dog, the other with the youngest kids. That also rules out other fun things you might want to do with the kids, like soft play or amusement parks, which are not dog friendly. Especially an issue if you have kids birthday parties too, the dog often won't be welcome at other kid's parties, there's always going to be a kid that's terrified or deathly allergic to dogs.
In the home, no matter how well trained both children and dog is, they can never be left in a room alone together. A real juggling act if you're the only adult in the house. It just takes one second, a dropped snack, a snatched toy, a stumble because they didn't see the dog behind them, or a sudden shout or scream, that can cause a dog, no matter how well trained, to react.
You also have to think of when kids come to play with yours at your own house, while your own kids may be "trained" on being around your dog, other kids won't be and may push buttons. This is how children get bitten :(
Spaniels, and their crosses, are notorious for resource guarding, which is a massive nono around small kids. Sadly this is why so many rescue spaniels and cockapoos can't be rehomed with small kids and why they've been signed over in the first place.
Research breeds carefully, take your time, dogs aren't going anywhere and will still be around in a few years time!