Gwen Stefani & Blake Shelton On a Date ... It's Kid Serious Now!

Gwen Stefani and Blake Shelton's relationship can't get any more real than this -- hanging out with her toddler son!

Blake joined Gwen and Apollo for lunch Thursday in Studio City, the first time we've seen them in more of a family type setting. Of course, Gwen has two older boys ... so Blake's not fully immersed yet, but it's starting to look like it's only a matter of time.

This should go a long way to quieting the doubters ... for a while, anyway.