There are 2 moing violations, plus a that much over the limit, the cop could have arrested him. I am not sure if they will allow traffic school. I am sure the total will be over $300.
As for cost, if you can go to school, then yes that will be cheaper. I still say talk to a lawyer as they can tell you if you evenqualify, odds are you can get that much advice free.
If you cannot get school, then the lawyer will probably be only $300. For the money he can probably plead it down to an unsafe lane change or maybe even a non moving violation. He did put 90 on the ticket, so he already did you somewhat of a favor.
Here is the thing though, if you try for school and they say no, you are screwed, $300? Wrong, add how much your insurance will go up for the next 3-5 years.
I would at least consult a lawyer and see what you can do.