The gobies should be fine with one another, provided they each have some space and don't need to fight over caves. The puffer is a gamble -- I don't know anyone who has mixed them with Redigobius spp. Figure 8s usually work fine with bumblebees, and so by extension should work with other small gobies. Certainly worth a shot, but make sure you have a Plan B in case it doesn't work out.
Cheers,
Neale