Carefully reread your notice of motion.
The charge you have is before the court and it cannot be amended or changed without the court's consent. Likely there is a court date on April 29 to hear a motion to change the charge to careless driving.
There are two issues that are raised. First, the Crown would not seek the more severe charge of careless driving unless they have information that warrants this heavy charge. You should have disclosure by now and would know why they are seeking the greater offence.
Second, as Radar Identified has stated, it is a much harder charge to prove. Why would they make it more difficult for themselves to convict you?
You need to be very strategic about what you are going to do about this. It sounds like either charge will require the witness to show up. At first glance [without knowing any specific details about what happened] you have a much better chance of fighting the careless driving charge.
If your only strategy is to plead guilty to a lesser charge than try to keep the lower red light offence and plead that down. If you plan to fight the charge, then take the careless driving charge.
BUT read this case R. v. Penketh, 2008 ONCJ 596. The important point is that the defendant did not testify and the defence offered no evidence. Don't make this mistake.
Your paralegal should work with you on developing your defence strategy.