I don't know where it is in the legislature (although if I have time tomorrow, I may search for it. I often read the legislature regarding animals just for fun), but I do know that it is illegal to take kittens away from mom until 8 weeks. I don't know if its just a California thing, and why California law should apply to you in Washington.
Anyways, please consider a rehoming fee for your little ones. You can take them to the vet to get their first shots, and then charge a fee to have your expenses reimbursed. Thats the least you should do as a
responsible pet owner. Or you could charge a small
adoption fee that will go towards paying for your kitty to be spayed. Either way, its risky business giving away free animals.