Do not listen to that guy regarding what is unreasonable to ask of dance students for a dance class. What is important to understand with shoes is the level of "grip" and "Slip" a suede bottomed shoe provides the proper feeling and ability to move. Taking Ballroom as a follower requires you to be able to have some slip and street shoes will never provide that feeling at all. Even smooth leather bottomed shoes might be too slippery in a gym or wooden floor. A 2.5 or lower inch chunky heel will work for standard and latin for a beginner. The character shoes you have right now will work just fine! You can glue on some suede (example link, dollar store suede patches will do just fine) to give you the correct feeling and connection to the floor. All you need to do is cut he right size to fit and you are GTG. I was a professional and I advised my budget students to do this or these are an option for you that are fairly inexpensive.