Don't you love boys! :)
I have 1 boy age 7. His buddies are over a lot and the toilet used to get pretty gross.
Here's how I eliminated the problem. When I see a mess or a "miss," the boy cleans it up. I give him a rag and homemade, non-toxic cleaner. Then they have to wash their hands with soap and water --again.
Kids will ALWAYS give you an excuse. I don't care- accident, on purpose, so what? We still have to clean up after ourselves, right?!
In any case, they've hit the target a lot better since!
Here's the recipe for the non-toxic cleaner:
Fill a spray bottle 3/4 full with hot water
Add a tablespoon or 2 of Borax
Add 1/4 cup of white vinegar
Add 1/4 cup dish soap
Mix and keep it on the counter for everything.
Non-toxic, except to urine and germs!