If I take pictures of my kids and their team mates at a little league or youth sporting event and other parents want to buy pictures from me, can the organization that is holding the event force me to give them any profit and can they threaten to have me arrested if I do sell photos from those events without their permission?
It depends a lot on the property in use. If it takes place on public property and they aren't allowed to tell people they can't be there, then there isn't much they can do to stop you, other than threaten to kick your kid out. Unless it is private property, they don't have a right to restrict what you are taking photos of in most cases.
That said, it doesn't hurt to talk with them and figure it out so there isn't confusion. Even if they don't have a right to stop you, they may try to if they don't know what is going on or you make them uncomfortable. You are far more likely to get an end result that works well for everyone by talking to them about it.
If you are doing it basically at cost, it probably isn't likely to be an issue. If you are actually looking to make money on the deal, they may want a cut, and even if you don't have to, it may be worth giving it to them, because if it works out well, they may ask you about doing it for other teams as well and could become a decent income stream for both you and them, if that's something you are interested in.
I'm not sure about little league but in the UK it depends on a few things so I will try to explain.
There are a lot of sports photo companies that travel to the larger events with several photographers to sell pictures to the parents. These companies will never gain entry without paying to be there and because of their existence, the clubs have learnt that they can earn money from such a thing so if you were looking to sell pictures back to multiple parents, you will no doubt have a fee to pay.
If you want to take pictures of your own children, your are perfectly in your right to do so.
I have often taken sports pictures for a single parent who has commissioned me to be there but I have always advised the get permission from the club. That's usually OK unless one of the larger companies are there and providing the insurance all checks out it is fine.
I suggest speaking to the club to check everything is OK to avoid any embarrassment on the day.
Caveat- I'm not a lawyer, but...
It is well established that you have the right to a) take pictures on public property and b) to take pictures of anything and everything you want and that c) you own the copyright for those images.
As long as the events are held on publicly owned property, you are in the clear. You should contact your local newspaper about this- I'm sure that they'd love to run an article about the attempts to violate your 1st Amendment rights. Also talk to someone at the local chapter of the ACLU for advice.
In some situations there are limits on how you can use your images, but in your case there's no problem since you're selling pictures of kids to their own parents.