My daughter has Asperger's Syndrome, and she NOW (age 20) eats everything. I am including black pasta made with squid ink, blue cheese, and rare liver. My rule has worked well. I never expect a child to eat food with lots of hot pepper seasoning in any form. But for everything else, they must eat (not try) one bite clearly visible with the naked eye. It has to be the first bite of the meal or else the seasoning hunger adds to flavor will be masked by satiation. Then I offer sincere sympathy that they will have a less than complete meal if they refuse more.
If the main dish is too spicy for me to offer it to the child, I considerately offer an alternative reheated old cold leftover. I have been known to give a child peanut butter on reheated white rice when they refuse our dinner. So be it.
The hardest thing to do it NOT engage in discussion or drama about someone else's preferences. I just happily lap up the food myself, and eventually, all are converted. My neighbor's picky son (age 7) ate the required bagna cauda pasta single fetuccine noodle last week with his mother looking anxiously on. She had implored me to separate out plain noodles for her son. (She lives steps from me, so starvation was unlikely.) I calmly informed him of the rules of our house requiring a bite. Two bowls of mildly flavored bagna cauda pasta later, he smiled and told me I was a good cooker. And had home made Cherry Garcia ice cream for dessert.
So try a bite first and see if you have finally tasted something enough times to like it. I believe a good cook will make such great food others will come to relish it. Ask my daughter, queen of I'll try anything and once very hard. BTW, 6 cup cupcake pans are great for feeding toddlers. Put in wee bits of healthy anythings and offer. Replentish what they eat more of.