That's awesome! It's so important to avoid processed foods, and eating for the seasons can be great! It depends where you are, though, you may still need to get imported foods if there isn't much that can grow in the off-season where you are. It's a wonderful idea though!

Temper tantrums. Lol.
Every child is so different, but I do think that most do tantrums when they feel they either have no control or no attention.
If it's for attention, not giving the tantrum any attention at all works well. You can't even bat an eye at it for that to work though. Make sure that the child is safe to flail and just ignore. If they don't get a reaction, what's the point?
If it's for control, ignoring won't work. They'll continue to they get what they want or tucker out. Let them get it out of their system, then talk to them when they're calm enough. Let them know that this doesn't work to get what they want, and tell them how they can. Then make sure to give the child a bit more control over other aspects of their life so they feel satisfied. It doesn't have to hinder you, an example might be that they want a t shirt on a cold day. Let them pick from a few choices of sweaters so they feel like they had control instead of saying they're going to wear a sweater instead.
If tantrums are successful, even with negative attention and bad results, they will continue.
It's not 100% lol but it's the best solution I've used since becoming a parent 12 years ago. :)