I imagine the topic is open to interpritation and as such I figured I could answer it both ways I considered approaching it.
One piece of advice I would like to impart to them is how important it is to have a dream, have a vision for what you want to do, how you want to do it and who you want to be your support network as you puruse that dream. Ultimately, take your time and consider carefully your options as you grow up and become career and family oriented yourself, and then come up with a plan. Planning is such an important part of life. A person with a plan tends to be more proactive and goal oriented. The potential pitfall to that is the often very real cliche that life does not always go as planned. So while having a plan is important, the ability to be maliable and bend or fold that plan with the little twists that life likes to throw at you is equally as important.
It's easy to say be a good person and love others, but to me, those things are all a part of a successful life plan. Enjoying yourself and the people you surround yourself with is what brings value to life. Personal pride and the love of friends and family are almost sure fire ways to happiness. Happiness and love is in the relationships we build. Be a loving person. Be a relationship builder. Work hard and enjoy the hard work. Life isn't just about the goal, it's also about the journey to that goal.
So ultimatley the answer to my first consideration leads me to my second consideration of the question. Something my kids should know about me will be that I followed my own advice to them. What has brought me the knowledge and advice I give is not something I have not experienced, but a path I've followed myself. I don't want to be a do as a say, not as I do parent. I wish to be a do as I say and do as I've done parant. I want to set the example and be someone they can look up to and be proud of. Someone who might not have developed the plan at the normal time or place in life when some others might have, but was willing to develop and grow and realize the fruition of his plan in himself and his children.