How about a way for the Builders to advance after all the buildings are built. Something like a rockfall that keeps blocking the stream. If it blocked it at a rate that would keep one person continually clearing it. You could have it similar to the Fire where it has Hours left. But in this case it could be hours till completely blocked. If a single builder keeps clearing it the timer dosn't change (Just sort of maintaining the cleared area) but if 2 or more were clearing it then the timer could increase such as 5 hours till blocked 10 hours till blocked etc.

Also have it so the children can learn from their foraging (Even at a slower rate than adults would be good) and can be set to pick mushrooms (Or whatever is collected) if they pass close to one on their general travels.

It would also be great if nursing mothers could do some work while nursing it would allow them to further their skills even at a slower rate while they are nursing. If mothers are still going to be the only ones caring for children then after they have 5 or 6 kids they should be master parents.