How do I get more food supplies after the berries are gone, and how long until the kids become useful. And how do I get those tech points up faster or can I not?

ok for a start, don't start breeding till you have heaps of food, most of your ppl should have been put to research so you can get level 2 in farming and start on the crops. There is no way to get faster tech points except to put building etc on hold and make nearly everyone research.

kids can start training around 13-14?
you have to upgrade your farm tech.
and only way to get tech points up faster is put as many people as you can on research.

But the farming can take along time for the crops to grow back after they are gone (usually about 100 minutes for me) so you also should research level three of the food so you can fish.

so are my people going to die because i've had 2 kids but Im almost out of berries and just starting on where I unblock the river

don't worry about the river. work on researching tech points for farming.

ok I have 4 people working on it but Im still afraid they are going to die

try the mushroom trick for extra food. pause the game (spacebar) and put all your children on the mushroom, and then unpause, they will count for more than just one.

doesn't that mushroom trick defeat the purpose of the game? to challenge you to manage your resources until you can get level 3 farming

It's all in how you see the game, I think -- to me, the mushroom "trick" is a cheat just like setting your system clock ahead. But then again, I also think that getting answers to puzzles from game forums is a kind of cheat, and it ruins the game for me.

But that's just me -- if someone is more interested in the result than the process, then they won't feel bad using tricks/cheats/walkthroughs and they'll enjoy the game as much as I do without using them.