Hi Jonas. Welcome to AP.

If you want to get close up shots of tongues etc you will need a different lens. A macro lens will provide a better choice of lens over the 18-135 which is a general purposes lens.

Not being a Canon person, I have no experience with their macro lenses, but I am sure others will be able to give you some advice on a specific macro lens for your needs. For third party brand lenses the Tamron, f2.8 90mm macro would be a good choice. Just make sure you get the right lens for the camera you buy. Third party lenses are made to fit most brands and you have to choose the lens to suit your camera body.