I think most people prefer PayPal because it is secure and offers protection for buyer and seller (when paying for a yoyo using “goods and services”).
I don’t recommend sending cash through the mail as, if the envelope is lost or stolen, you are out the cash. It would be better to ask your parent or guardian to either write a check (you can give them the money), or to use their credit card to pay through PayPal. Using PayPal is safe, the person receiving the money never sees any credit card information, they just have the funds appear in their account.