NO! Do not cave in! Kids are developing their taste buds. Sometimes HOW it's prepared is as important as what. i.e. frozen peas vs. canned peas (texture) raw apple vs. applesauce. Adults have issues w/ textures too and always will.
Get a copy of FEED ME I'M YOURS by Lansky. This will give you lots of ideas. How about a baked sweet potato w/ a little butter (NOT margarine) and some pumpkin pie spice or cinnamon?
KEEP trying new things. I teach nutrition to 3-4 year olds AND moms. You'll be amazed at what they'll WANT to try if you DONT talk about how much you dislike something and continually try new things, too. Talk about how much FUN it is to try new things.
When they refuse to even try, talk about how much they're missing out. REPEATEDLY talk about how good & yummy something is. ASK/REQUIRE a "courtesy bite" of EVERYTHING. Get in the habit of this. You made the effort to prepare, they do you the courtesy of at least trying.
When they won't try, ask them what they DO like. How do they know? Of course, they TRIED it. They'll never know unless they try.
If they DONT like something, acknowledge that they made the effort, thank them for trying and remind them that they won't like everything.
Talk to them about nutritional value.....carrots & sweet potatoes help us see better; cheese, milk, yogurt help make our bones strong, etc. They need (LIKE ADULTS) to understand the WHY to make it more appealing. If you don't know....RESEARCH. You'll be doing EVERYONE a huge favor!
Make sure you LEAD BY EXAMPLE!