Building circuits takes some time and buying is sometimes cheaper than you get the parts for. There was a time where I liked to build circuits because it was fun and was a learning opportunity. But now with everything you can buy out there, you can be well on your way to doing some more interesting things.
I like to purchase a lot of my electronics projects from Amazon. You can get deep into their integrated controllable circuit systems. Those are fun to use and can help you teach your kids a lot about electronics. Snapcircuits is a great learning aid for kids if you do it right.