You should be able to use TA after you've been on your first ship for about a year. I don't know if you can use it for child development, though. I know they "encourage" you to get a rating related degree, but I don't know if it's actually mandatory, but you will have to file a degree plan with the ESO or navy college office. You can also use NCPACE when it's available, which is usually on deployments. If you go to a carrier, you will also be able to take online courses, even when underway. I recommend you sign up for the GI Bill, then you'll have college money available when you get out if you need to finish your degree or want to start working on a Master's degree.