I don't know about the numbers but I have found that you can sustain a village of about 12 with just the trees, the honey and mushrooms as long as you keep the kids collecting mushrooms fairly regularly. If you keep an intense eye & consistently double or triple up kids on the mushrooms, and pause when you're away (even for a short time), a village of 15 to 17 is possible, but anything higher than that and you'll start running out of food.

There are so many variables though; like how many red mushrooms you get, whether you have a chief make food & what events happen I had an event wipe out all of my food early in one game and it was very hard to get the bin looking healthy again, in another game my hive was completely refilled just as it had started running out, so there was almost 500 more food available in one instant.