Hopefully that is the reason I am having kids for someday :/
Kids!!!! Always the ungrateful bastards will never get interested in bonsai. Seriously, it is a mistake to assume any of your kids would get interested in your hobby. Sometimes they do, but it is much more rare than you might think.
But in time you will make "bonsai friends" and possibly even mentor a bonsai novice or two, and as they learn, you will move trees along, out of your collection to someone else. Don't think of your collection of trees as being "until death do we part", think of yourself as temporary custodian. Plan on moving everything along at some point before you are too old to take care of them. Think trees come, trees go. And then there is the buy-sell-swap-trade. I always have a tree coming or going.
With seedlings, you are bringing them through a phase of their development. And if you really are only 16, you have many many good years ahead of you to develop seedlings. And if you are my age, over 65, I still start seedlings. And damn it, I intend to see them at the Nationals some 30 years from now.