Well, there actually does exist a special tool to clean the Wii's laser. It was made by Nintendo for a while, then.. mostly vanished as they stopped making them. But, to my knowledge, you should be able to use a regular laser cleaning disc such as
this one on Amazon, so long as you have some homebrew app that'll play music CDs. There's also
this video on Youtube that shows you how to make a tool like the original Nintendo cleaning tool, but it seems a little more.. janky, to me. You can also take the console apart if you have the know-how, and open up the drive, then clean the laser with a bit of rubbing alcohol, and a q-tip. That's how I clean original Xbox DVD drives, and it's served me well over the years.
Anyways. I hope that gives you some ideas on where to go from here.