I don't get what the big deal is. I don't think it's rude that servers encourage kids to try new foods. The last time I ate at Ohana, there was a table next to mine with two kids, the mom asked if there was anything else available for her kids, and the server said she'd get them pb&j, but why don't they just try this food first? She didn't say it at all rudely, but instead encouraging the kids to try something new. They did, and they liked the food.
If parents didn't give in to their kids so much then there would be far less pickiness when it comes to food. Case in point, me and my cousins, my little cousins always got their way when it came to what they wanted to eat, and now they're adults, and they are still very picky. At Thanksgiving all they would eat was turkey and mashed potatoes, no veggies at all, so that isn't even that healthy.
I'm not saying children should be forced to eat stuff they don't like, but they should be made to try it, they will usually like it.