They have offered you an interview, so they know you can do the job, it costs them time and money to interview people, so they only bother with the best few applicants.Try not to worry about the gap in your work history, most people have at least a small gap from time to time, [unemploymnent, leave to have kids etc].
As others have said, it depends on the job what you tell them, ie if the job is with an NGO or any sort of caring role, your experiences could be seen as an advantage in the role.If you do decide to be economical with the truth, tell them you were doing something that you have done, but at a different time, ie if you toured Europe in 1992 for example, tell them it was 2002.

It could be worth having a chat with your local Careers Service , or whatever they are called where you live, see if they have any better ideas, there number will be in the phone book.

Good Luck.john