I know you didn't ask for this type of opinion, but I really think there is something to be said for paying your own way in college. I don't mean paying 100% as that is pretty suffocating but contributing SOMETHING...so that you are a partner or an investor in yourself.
My parents agreed to pay half my tuition, half my books, half my rent up to $200, half my car insurance and nothing else. Food, gas groceries, bills etc was up to me. I think this was a pretty good deal because it made me really think twice about which classes I really "needed".
I had friends who would sign up for a summer class, decide to skip a couple days for a summer trip or something, then come back and bomb a test and so they drop the class with no refund to avoid a bad grade on their transcript. I NEVER did anything like that.
I had calculated how much each hour of instruction was costing ME and always showed up on time because I was paying something like $10 an hour of my own money (plus interest) to learn what they had to teach me so DAMMIT, I was gonna get my money's worth. I had lots of friends who either had free rides from FAFSA, sports, or mom and dad and they strolled in when they felt like it, texted their boyfriends during lecture, slept during class etc. they just basically did the minimum necessary to get a B. They weren't investing in their own learning, they were completing tasks to keep the checks coming and accumulate credits toward an arbitrary degree that many of them had no idea how it would make them any real income.
now, I'm not suggesting your kids will do this (though let's be honest, the might) but my parents had enough money to put me through 4 years of university without batting an eyelash. But they both worked their way through college, and wanted me to build the character that comes along with that.
As a result I chose to take my first 2 years of pre-reqs at a community college before completing my degree. I worked 15-25 hours a week at Starbucks and paid as many expenses as I could as I went (I also got some tuition reimbursement from Starbucks which was a nice perk). I came out of school with $13,600 in debt and a professional license that earned me $57,000 my first year. Now I earn $92,000 a year off that same frugal 4 year education and haven't had student loans in many years.
I realize you may be looking for tax shelters, but if you end up not using it all you'll be worse off. And it will be hard to "enforce" your rules or ideals about how you want your children to behave in college if you've got the underlying worry about "all this money" sitting tied up in an account....you won't want uncle sam to get it so you might tolerate less than scholarly behavior as a result...
Just a thought.