Thoughts and vague suggestions...
If you mix C++ and Visual Basic, your program will be harder to upgrade and maintain. :(
Experiment with both languages. (You would have to buy Visual Basic.) Write a program in both that opens and dislays a bitmap. You could use one language, and one of your coworkers could use the other. My guess is that Visual Basic will "win". My boss seems to whip-out VB programs much more quickly than I could write a C++ Windows App. (Neither of us are full-time programmers; We're hardware guys. We both know command-line basic, I don't know Visual Basic, and he doesn't know C.)
Do some research to find out the difficulty of converting/handling the various file formats in each language. Any "visual" or windows compiler will have functions for bitmaps. If you find a compiler that has a built-in library for handling the various image formats, you'll save lots to time!
This a C++ board so there may be some bias. :)