Will exclusive worship of Krishna offend Ganesh and Shiva?
No need to worry. You can worship both Ganesha and Shiva as assistants on the path of worshipping Krishna. They will certainly not be offended if you realize their true position and seek their help, association and guidance in becoming a perfect devotee of Lord Krishna.
Also Srila Prabhupada said that Ganesha can remove the obstacles on that path of Krishna consciousness. For this purpose, many Vaishnava temples—especially in India—feature forms of Ganesh at their entrance.