The duo will compete in the under-19 event in Bulgaria which takes place between July 18 and July 24.
Denton, who is still an under-17 athlete, impressed at last year’s Youth Olympic Games in Argentina, finishing eighth, despite being one of the youngest athletes in the field.
Mitchell has significant experience at international youth level and competed in Bulgaria at the 2017 Under-17 European Championships where she finished as the top Brit in 11th.
Meanwhile, former Plymouth College pupil Myles Pillage recorded his best ever junior major championships result with a 10th place finish at the Junior Worlds as he led the British men’s team home in Drzonkow, Poland on Friday.
Pillage was leading the field after the fencing, swimming and riding disciplines, but his hopes of a medal went in the laser-run.