If you want your parents to have 100% control of the money, ask them to set up a brokerage account you can send funds to.

If you want some control over it, you can set up a trust. It really depends on how much money you are talking about and what the goal is.

Edit: also, you have to file if you go over the annual maximum (x 2 if you gift each parent). Current maximum lifetime gifts before taxes is $12 million.