I doubt you'll find any 14 y.o. mountain bikers that ride Delcastle and read this forum. I ride in northern Delaware a lot, but I've never ridden Delcastle. Didn't even know it had trails.
There's a lot of good riding close to Delcastle. Have you ridden in White Clay, Middle Run, Woodlawn, Fair Hill, or Iron Hill?
White Clay - Probably the closest AND the easiest to figure out. If you're close to Delcastle, you might be close enough to ride into White Clay from home. If you're only 14, that might be important to you. The trails are well maintained and marked. Free map at the park office.
Middle Run - Lenape Trail loop is a good ride and easy to follow. It has a connector that joins to White Clay's Brian's Farm trail.
Woodlawn - Close to Delcastle but it can be tricky to figure out the legal trails.
Fair Hill - Big place with lots of great riding. Lots of horses = lots of poop on the trails. Too far to ride and it's around $5 to park.
Iron Hill - Small park in Newark, free parking, and has the mega-dip which is pretty cool if you've never been there. **Warning on Iron Hill** Watch out for the *****. They aren't shy about who sees them "gettin' their gay on." And don't let the used condoms stick to your tires.
Oh, and by the way, it's "Delawareans."