You've been on here 4 years and never signed up to a workshop? Get on it! Nothing to loose and everything to gain. It'll be worth it.
In the mean time, dont get yourself worked up and anxious about the trip as this will set you up in the wrong way. Telling people can help, but if its quite a few people then it may not be the best way. It all depends on how you feel about it.
If you want piece of mind and a gauranteed way of going, see your GP asap and get an appointment with a urologist to obtain some catheters. Quick, easy to use with only disscomfort to deal with. Chances are you wont ever need to use them as having them on you reduces the anxiety anyway.
All the best,