Paul, I've been asked to shorten the links as far as the text shown in an invite where I've had to explain how that is an issue with copy and paste. I'm no expert but I don't think you can have copy and paste show one thing but paste a longer link. When I've dealt with this issue in the past I've used my survey website which provides a much shorter, simpler link. I've just created a second page for my website and used that (ie www.mysurvey.com would use www.mysurvey.com/survey1). I could then set script to automatically redirect that page to the correct link of the survey. Now that would obviously only work if you only were using a generic survey link. So what I have done instead is provided the generic link but then listing the password they would have to type in separately once it took them to the log in screen.
Probably nothing you don't already know but just passing on what I've done to deal with similar requests. I've also used this method for our call center when they wanted to be able to provide a url verbally over the phone.