The whole vinegar thing is murky without a lot of solid evidence either way. I do use it myself, but it's not organic and it doesn't have the "mother" in it.
As ChickensAreSweet noted make sure your heat lamp cannot fall into the bedding, most especially if you are using one of the big 250w bulbs.
Brooding chicks isn't rocket science. You don't have to control the temperature to the degree, just get it close. The chicks will tell you if they are too hot or cold. This is what you should be looking for:
Do keep the water clean and fresh. Make sure they always have feed available, a fresh, quality chick starter. Put a cover over the top of the brooder because they'll soon be able to fly to the top.
Enjoy your birds!