Some riders like technical routes, others, often beginners and older cyclists, prefer milder stuff. I think it is a valid question to ask before participating. You should be happy that your event is getting interest and replying to possible entrants with as much info as possible. A big problem with races and trails in general is the lack of a sensible trail rating system, at least the ones I've ridden. One person's blue is another's red or even black. Trail running has an excellent system which tells any entrant the exact nature of the trail. Skiing also has an old and well known system. Either could be easily adapted for mountain biking. Have a look at the: Wildrunner Trail Grading System.
