Who buys Kennedy half dollars?

It depends on the date and condition.

If you have any from 1964 to 1969, they're worth more for their silver content than as collectibles. in 2001 1964's would retail for about $13; the others for about $5. Of course unless you have a large quantity, a scrap dealer will only give you the lowest wholesale price.

If you have any dated 1971 or later, only proof or uncirculated coins have any extra value; you might try going to coin shows and seeing if anyone is interested. If they're ordinary circulation issues, just spend them.

Yes, spend them.And then someone else will be asking the same question!