Perspective.... this question is all about perspective. My little guy was a healthy eater until he went through cancer treatment from 16 months old to just over 2 years old. During that time the "food" issue was really put into perspective for me as I learned about all different ways to get nutrition into his body. From organic, to liquid, to G-tube feedings of special formula, to IV nutrition... we kept him alive. And there are some basic things that I learned that are priorities.
1. stay hydrated (32 oz per day for a kid his age)... don't deny liquid nutrition (milk, juice, even soda pop) unless it's right before a solid meal. Water has no calories and doesn't hydrate effectively. Pedialite has electrolites but it can cause diareah which can lead to dehydration. 100% juice is the best way to go. And milk has even more calories.
2. don't worry about the whole "organic" issue. Too often we are pressured to buy altertative products that seem like they are better, have more vitamins, etc. just because they are organicy (goat milk, no-hormone, organic grown). But, believe you me... I read labels and spent a lot of time working with the diaticians just to keep my baby boy alive. The bottom line is that everything breaks down into the same stuff and if you're child has a healthy normal kidney's even some of the chemicals we ingest won't do a darn bit of damage to him. God gave us kidney's for a reason.
When a little guy is not getting enough nutrition calories because he's not eating solid foods, go for the fat in the liquids that he drinks, the fat breaks down to lipids. Give him the bulky, creamy, high calorie drinks. There's no harm in adding extra liquid vitamins in his juice, milk, or Danimals. He can live on that alone and be perfectly healthy & chubby.
Another fatty calorie addition is to put about 2 oz of heavy whipping cream (from the carton) into his milk cups/bottles, on cereal, in all of your cooking (like pancakes). Use heavy cream. It actually has less sugar but more calories.
The goal is to sneak in as much calories as possible in the most consitant way that he eats. And if that is by liquid drinks for now, don't worry about it.
3. No liquids before meals. I don't even serve a dixie cup of water with my kids meals because they so fascinated with sipping water that the don't eat. They get a drink when they are done eating... or if I cave in... I keep a tight control over their sipping by not leaving the cup/bottle on the highchair holder. And we eat together, all nibbling together, so that they can see each other enjoying the solid foods.
4. Do what ever it takes... one little guy I knew only ate by snacking. He snacked all day (a cup of cherrios, 5 ritz crackers, 2 slices of cheese, apple slices dipped in peanut butter, a sandwhich wedge in hand as he played,etc.) He rarely sat down to eat, but he snacked all day on the go. And he stayed alive.
My son, bless his heart, went through a texture phaze as he was learning to eat by mouth again rather than G-tube feeds. He would only eat creamy soups; nothing scrappy or hard. Your son might have some food texture sensitivity at times.
So, overall, my advice would be...pump him up on calories, sneak vitamins into everything (even add a liquid dose to home made cookies),and give him what he wants and how he wants it. There are priorities that you will understand as his parent no matter what other people's judgments & ideas are.
One more suggestion... I put protien into just about everything I cook also. There's soy protien and whey protien. It helps to build muscle and there are also even more vitamins in the powder. I put it in all of my cookies (oat meal, sugar cookies) and in pancakes every time. You can also buy pure DHA for children, which helps brain development and is the same stuff as in formula. I just pierce the little capsules and sqweeze them into the juice bottles.
And only one warning... a lot of the high calorie drinks like Danimals for example have so much sugar or high fructose corn syrup which is linked to cancer... So, what I do is I dilute those kinds of flavorful products down with the more natural stuff like the creamy yobaby yogurts. That way the kids still get their flavor that makes them drink it all down, but, also they are filling up on more healthy foods. I would look at the sugar dose on the Carnation... for that purpose too. Just to see if the sugar is something that is worth adding into your son's diet.
Most of all...pray. There are many good reasons why we are instructed in the bible to pray over our food. God sancitifies it and sets it apart for our nourishment. There are even stories in the bible where believers were saved from disease and illness because the food was blessed. Honor God, thanking him for his provision, recognize him as the provider and your source, and he will bless the food, helping it to go and do all that it's supposed to do in your body and your families body so sustain your good health, heal you, and nourish you.
God bless, YM