Jenn D, regarding your question, my wife and I have three children. We are saving through a PA state 529 plan. We are on-track to have saved enough to pay for about 1/2 of each of our children's college education assuming they attend top 4-year universities...in other words, we will kick in a little over 2 years for each child.
Each of our children know this (oldest almost 14, youngest 6). They each understand that if they want to go to school it will mean part-time jobs during college, full-time jobs when out of school, no Spring-break trips, and likely college loan debt.
My wife and I have also counciled our oldest on the financial sense that attending a 2 year community school and then transfering makes, and how if he went that route it could mean much less debt, more spending money for them and a general easier time financially. We have discussed the pros and cons of being a transfer student. We have had this discussion with our oldest because part-time jobs, cars, dating, and more expensive "toys" are looming large in his future.
So, to answer your question, I say make your kids aware. Make it sort of a "contract" between them and you. Let them know what you are doing for their future, and what you expect from them, now, and while in school to make their college education a pleasant reality.
TJR