I haven't done this at Disney, but I do often at home. DH works a lot and I am off all summer so I'm kind of a single mom and we go to alot of buffets. I usually have both kids stay at the table while I get their food and once they're eating I get mine. Now I am sure I'll get flamed for leaving my kids alone for even a minute, but realistically sometimes there's not much choice. I figure my oldest (7) helps keep an eye on my little one (4) and there's more safety if they are together. I also give my oldest a "job". other than watching his brother, like keeping an eye on my sunglasses or something. He's very into being grown-up.
In addition, if you alert your server, they are sometimes willing to keep an eye on them casually. That keeps the illusion going with a little more afety.