The Arduino software scans the files for function prototyping and include files before compiling.
There is an error with that, it doesn't look at the "#ifndef", so you end up declaring "hello button" twice.
Could you try to remove the includes from all files.
Use only this in the *.ino file:
If you get an error, perhaps you have to include one more in a file.
You probably don't need to do the prototyping in the *.h file. But it's okay, so you don't have to remove it.
Please declare the helloButton in the *.ino file.
Creating a class in a *.h file could easily cause problems, I try to avoid that.
If you are making a libary, you have to include specifically what is used.