it'll take forever to grow a bonsai from seed, but the ones that you have will be a fast growing tree I'm sure. I has some, that were cherry I think, a few years ago. I planted them, they germinated and got to about 2 inches tall. I didn't water them enough, they died. I'm sure you could get a little tree to prune in a couple of years though
I now have a lovely bonsai birch tree outside that I bought in a garden centre, it's a few years old now and is doing well. Nice sideways branch structure and pretty golden leaves in the autumn.
keep any trees you get outside and water in the summer. prune them once a year to get the shape you want and it'll be fine. It will still take 40 years to get a really cool looking bonsai.