I don't know if this helps but I know a few others like your DC. Their FSIQ were well over 140 but they were just not all that academically driven and they stayed under the radar at school. They coasted throughout their prep school career and they didn't do much more in college. One of them went to a law school only because she didn't feeling like working.
On the other end of the spectrum, I know someone who won every single STEM award in the state for 4 straight years in high school. He was always extremely driven but his younger siblings were not as high-profile although all of them are most likely at least HG+. I think it takes more than high cognitive abilities to strive towards exceptional academic achievements.
If I learned anything from my friends who have raised GT children who are now adults, is that with some of them, you have to push a little bit to find something they find challenging and rewarding that could lead to a career. A boy I know was floundering but his middle school science teacher saw his talent then talked his parents into sending him to a NASA-sponsored summer camp. That really turned his life around and now he is on a full scholarship in college and doing very well.
Both of your DC are still young. They have many years to find their inspiration.
