Sewing it would be the most secure way to keep every thing attached. It you decide to go with glue instead (or along with it) I would use Fabri-tac from Beacon Adhesives. It's probably the best fabric glue out there. It dries fast, clear and permanently and is very sturdy. The problem with gluing it instead of sewing it is whether or not the glue will come off when the fabric is stretched. Maybe take some scrap lycra and glue some things to it and then stretch it out to test it. Best of luck...I hate lycra.
In like a bolt from the blue, it's time for the reaper review.
Claves - Eternal Sonata
Aerith - Final Fantasy: Crisis Core
Rhyme - The World Ends With You
Megara - Disney's Hercules