My daughter had her heart set on doing CDE's for a few years now with Relic who's turning 20 because he just loves that sort of stuff not mind numbing for him like arena driving but unfortunatly looking into it more our chapter up here doesn't allow stallions to compete...bummer. Did get the chance a few weeks back to see first hand what it's all about and l know it's something that interests me. We're hoping to give it a shot with my gelding and a mare this spring if the dates work out for us..
Check out www.minicruppers.webs.com. It's a New England group of folks that do more ADS/CDE/trail driving type stuff, as opposed to breed shows. The site has a calender of mini-related driving events and clinics-lots of good info about where to go and watch or volunteer to learn about carriage driving with your minis.
CDE is basically the driving form of Eventing. There are three phases, Dressage, Marathon which corresponds to Eventing's cross-country, and Cones which is the equivalent of show jumping.
Check out the Lil Beginnings driving forum for more info on CDEs and other types of driving. The American Driving Society (ADS) is associated with many CDEs and they also have other driving events you might like, from Pleasure Driving Shows to ADTs (Arena Driving Trials) and Continuous Drives. Check out their website too (google American Driving Society).