It is absolutely not too late! Perhaps you could take a little time to come up with 3 or 4 specific questions to post. I've gotten great ideas in the past.
You mentioned "they will not eat on their own sometimes." I'm guessing that means they want you to feed them? That would be exhausting! I think that would be exhausting if you only had 1 child.
My situation is a bit weird, because I haven't fed my kids since they were about 10 months old. They won't let me. If they could have said "I do it myself" when they were that young, believe me they would have!
I learned very early on to simply place a plate of food in front of them. If they wanted more, no problem. If they didn't want it, sometimes I would offer them something else (judgement call) and sometimes that would simply mean they weren't hungry.
Try not to worry about whether or not you think they are eating enough. At 6 years old, they will not let themselves starve, and they will learn very quickly that if they want to eat they will need to feed themselves.
Not sure if that is what your situation is, but I hope it helps.
Please know that you are not alone and that you CAN do this. Good luck!