My daughter at a LOT as a toddler. She would eat more pizza than I would at one point. She wasn't small, she was at the top of the charts and I did become somewhat concerned about weight, but apparently that's what she needed at the time bc she slimmed out between 3.5 and 4 and at some point she started eating a lot less, now she will eat a slice of pizza or less, for ex. She definitely eats less at 4 than she did as a toddler. He may be needing all that fuel to grow. If he's always been at the 5th % that may be his normal. Are you and dad small? Is he young 1 or almost 2?
I'd suggest that you make sure he is having protein and fat every time he eats. Pancakes, fruit bar and banana is a TON of sugar (and even more if syrup is involved!) and not much else. Starting the day that way will set off a big sugar cycle of ups and downs, and at the down point he will want another sugar/carb snack and it just repeats. Combining complex carbs (whole grain, veg, etc) with protein and fat will even out the sugar release and make a big difference. Whole wheat pancake with flax and pumpkin in it or something like that adds a bunch more fiber, protein and good fats and would be much more sustaining than a white flour pancake, for ex.
I do think we have different nutritional needs at different ages and toddlers seem to need more carbs than the average adult but definitely try to up the protein and good fats.
I think if you are offering only (or mostly) healthful foods to kids (and of course check with the pedi to make sure there isn't a health issue) then they take in the fuel they need. If they are getting juice and crackers all day, then not so much, they could just keep eating that combo forever bc their bodies will be screaming for more sugar as their blood sugar crashes over and over. It is definitely not all about weight at all!