[X] Travel to the Jedi Temple on Coruscant.
Jango did not sit on Kamino all the time. He went out and did some clean-up jobs and recruitment drives early in the project, when helping hands were still unavailable. He could think of a reasonable excuse to leave for a short time and even have some trusted men cover for him if he does so quietly. Since he knows who Palpatine is, he may even witness first hand an attempt to bring him in.
Calling is dangerous due to bugs and a wandering Jedi is no guarantee. Giving a perfect stranger met by chance such galaxy-altering news is just plain stupid.
I don't see how calling is dangerous.
Just have Jango says that the new Clone Army is ready for inspection and wash his hand off of it.