Hi Lars,
The forced ventilation kit will help move the air around and reduce condensation in humid weather. It will also help flush out warm air after hot days so your telescope will reach night time temperatures more quickly.
However I find I get the most condesation problems when the mount and telescope have been cold for a long period, say after a prolonged period of cold weather, then the weather suddenly warms up. The warmer air carries more miosture and this condenses on the cold metal surfaces and even the optical surfaces. Additional ventilation at this point only makes things worse by supplying more moisture laden air to condense on the cold surfaces. Heat or dehumidification is the only way to resolve this situation. I said in an earlier post that I previously used small tubular heaters to reduce the condensation issues but have recently reverted to dehumidification which works perfectly and for a cost lower that the ventilation kit in your link.
Peter Carson