How low a fluid intake can i allow my refusing 6yo (with trach, no gtube) to be (ounces)? as long as he still pees, will we need iv fluids?

Depends upon: For an average weighted 6-y-o child (22-25 kg) , minimum fluid requirement would be 51-53 oz per day. If he still makes good urine output, IV fluid supplement is not required. Make sure he is not losing weight.

Be creative: The fluid value of some other items may be able to make up any deficit in straight fluids. Things like applesauce are 95% water, most steamed vegetables about 65%. Soups & broths higher. Sometimes you can find a novelty drink like peach nectar that will be tasty enough to be acceptable. Good luck.Peeing every 6-8 hours would be my minimum before i'd worry.