In the state of Arizona, once police are called the purported victim cannot have the charges "dropped" b/c the government takes over on place of a victim. You can however work with your son's father's attorney to advocate on his behalf. Unfortunately, he is facing mandatory prison time.
Mr. Cantor is correct. At the arraignment you should plea "not guilty" and request a public defender. You will then get another court date where you'll meet with the public defender and hopefully get you diversion. From what you've posted, that shouldn't be a problem.
The other attorneys you spoke with were trying to scare you into hiring them. Don't worry yourself too much and let this experience be a lesson to you.