Two kids. All assets split 50/50, as measured at time of death. Currently, funds go into a trust, which pays their living expenses, pays out in chunks at specified ages, like 18, 21, 25, 30, and then also allows the trustee to make discretionary payouts for something like college tuition or a house downpayment.
Our kids are getting older now (oldest is 18 and appears infinitely more responsible than when we wrote the will), so we may change that as they mature. If they both hit say 25 and seem responsible, we'll probably just drop the trust entirely.
One note: trusts are very useful for preventing an 18-yr-old from blowing through all the money. But if you set up a trust, please remember to change the beneficiaries of your 401(k)s and life insurance policies and such to be the trust. Accounts with beneficiaries go right to the beneficiary, no matter what your will says. So it won't do you much good to set up a trust to manage your million bucks in life insurance if your kids are listed as the beneficiaries on the insurance policy -- that goes right into your kids' pockets.
Finally, OP: please forgive yourself for blowing through what you received at 18, and don't let your regret lead you to over-control things for your kids. The most important thing is to teach your kids responsible money management and good money habits. You did what you were taught to do, because no one taught you better. The best thing you can do now is teach your kids better. It doesn't guarantee they won't make bad decisions, but it's the best safety net. And sometimes, bad decisions are the best teachers of all; after all, you recovered from your mistakes in spending your own inheritance, and somehow that journey led you here, right? So set up a trust, put some reasonable conditions on it, and then trust that even if your kids make a stupid decision along the way, they will learn from it and become better humans as a result.