As you stated in the question, there is some controversy surrounding the mutagenicity of ethidium bromide. However, a recently published opinion piece titled "The Myth of Ethidium Bromide" quickly dispels most of the uncertainty:
Ethidium bromide, as far as can be told from the data, is not a human mutagen. It’s not a mouse mutagen or rat mutagen either. Nor apparently a mutagen in cows and other farm animals, where it’s used in veterinary medicine at concentrations one thousand times higher than the red solutions that are so feared in biology labs, seemingly with no bad effects.
This knowledge does however not give us clear directions as to how the clean-up and decontamination should proceed. For this we can turn to the Material Safety Data Sheet (MSDS).
The relevant sections are Hazards Identification, Handling and Storage, and Exposure Controls / Personal Protection, numbered 2, 7, and 8, respectively.
Hazards Identification tells us that it's fatal when inhaled (in its solid form). This means that when it's not in solution, you should be wearing a respiratory mask or have a fume hood panel separate you from the dust. The fume hood should be operational, of course.
Handling and Storage states that you should:
- Avoid contact with skin and eyes.
- Avoid formation of dust and aerosols.
- Provide appropriate exhaust ventilation at places where dust is formed.
Finally, Personal Protection informs us that you should be wearing a lab coat and glasses (duh), but also gives us some data on the breakthrough time of the substance through nitrile gloves, which is 480 minutes. There is also a section on respiratory protection, but it is prefaced with "Where risk assessment shows [respirators] are appropriate," which is something that you must decide for yourself.
Thus, the answer is, as almost always, it depends:
In any case you will want to avoid brushing and dusting off the contaminated surface to reduce the formation of ethidium bromide dust. Personally, I would recommend to wipe all surfaces first with water (according to Wikipedia the solubility is 40 g / L) until clean using paper towels (and gloves, of course). Following that, one final wipe-down with ethanol may be appropriate, but that is left for you to decide.