Myself,
Do you worry that their work ethic will be challenged? I think having to find and immerse yourself in a career is a great opportunity and wouldn't want to do anything to take that away from my kids. Having a financial need to work is a good way to ensure they take it seriously. I had a friend who knew that at age 40 he was going to come into a big inheritance. He never really got his career started, despite going to a great business school, etc. He just had a little PC consulting business that he'd had ever since college and bumped along waiting until age 40. This lack of need to focus, and lack of accomplishment undermined his self-esteem, estranged him from his peer group, and left him too much time for 'hoosgowing'.
When age 40 came around, he discovered to his great dismay that the hoped-for inheritance had been largely frittered away by ill-fated investments made by his father/trustee. Around the same time he contracted a terminal illness and died in his mid-40s, possibly hastened by his fast-lane lifestyle.
I know your approach is that the kids have their savings early and directly, so that is better, I think. But if they were truly FI/ER right from the get-go, it could have undesirable consequences, unless they use that financial cushion as strong shoulders to stand on to reach even higher. Examples might be using it as money to start a company, or buying an apartment in a city where they can get into a high-achievement career or something along those lines. One way it could work is that the child could go into a low-paying but highly meaningful/satisfying avocation, without having to sacrifice a nice lifestyle. But any way you slice it, I think the kid should be urged to take career preparation and pursuit seriously for their own happiness. That is what we're trying to do with our kids (who will also start life with a nice nestegg, mostly from their grandparents, though, and not their own hard work)