Renting for short periods

Other

I have been approached by an agent asking if I would be interested in letting a property near the Olympic site for a period of a few weeks during the Olympics The extra money would be very useful.
I think that my mortgage does not allow holiday lets and I wonder what is the best way of dealing with this one and if it would be ok just to have the usual AST for a few weeks and assume that they would not want to stay six months anyway because they would have to pay above market value for it if they did decide to stay on.
What would be the minimum lenght of time that you would recommend for an AST or do you have any other suggestion?
many thanks