Paypal especially has warnings when you choose the donation button that you must be a organization with the proper certificate to qualify for legal donations.

Otherwise you cannot use the word donate in any of your text.  You have to use the term "gift" not donation.  

What i did was i made a normal buy now button, then changed the image in the code to my own button that says please helps us with a gift.

You also must have this line in your text if you are NOT a qualified donation company.

"Gifts are not tax-deductible, and we are not a 501(c)(3) entity"

They are really cracking down on this hard.  So do your homework and display it properly to save yourself alot of hassle.