Vitamin and calcium suplementation

I have two Uros and a baby Longicauda boa. Every time i sprinkle powdered vitamins or calcium on their food, they don't eat it. I guess they don't like the taste. I use a Reptisun 10.0 UVB light and put them out in the direct sun a couple times a week. Should I be concerned about them not getting their vitamins? They seem happy and healthy.

I have have also read that it's a good idea to sprinkle vitamins on the occasional food item fed to snakes. My concern here is that it will foul the snake to the food item for future feedings. I mean vitamins taste awful. Is there a solid reptile multi-vitamin that can be put down the throat of the food item so the snake won't taste it while eating?

Wayne