Definitely not... but you need to be use only the
minimum amount of air required to create an adequate seal. That seal should be to a leak somewhere between 20-30 cm H20 of sustained pressure depending on which text you consult (meaning above these pressures you should have a small leak, which is fine in pediatrics). If you place a cuffed tube and have no leak above 30 before placing any air then you have too big of a tube in.
You would be surprised about how little air you need, since the narrowest portion of the airway is at the cricoid for small kids. In the OR we use the ventilator circuit and in the PICU they/we use a Jackson-Reese/Mapelson circuit to assess this (only for kids < 2 years old). I am not sure of what equipment is readily available in the typical Peds ED. An Ambu/BVM with CPAP attachment could work as well I suppose.
Once they get above the age of about 6-8 you have more safety since the narrowest part of the airway progressed to the glottic opening as in adults. Didn't mean to be condescending (and I apologize if it came off that way), just trying to promote safe practices.
This article goes into this a little bit more (isn't directly applicable as nitrous oxide is used as an anesthetic, but the principles are the same). It also addressed the changes in practice over the years from uncuffed to cuffed tubes in the discussion section:
Laryngeal mask airway and tracheal tube cuff pressures in children: are clinical endpoints valuable for guiding inflation?