Some schools say you don't have to disclose info about "minor traffic violations." Check the language at the places you are applying/have been accepted to. Depending on the school and the nature of the traffic violation, you may not have to disclose this and it won't matter.
Even if you do have to disclose, if the violation is relatively minor it may not matter anyway, especially if your explanation of the circumstances is reasonable.
If you need to inform schools and you think the guilty plea, even with an explanation, will make you look like a law-flaunting, immoral or unethical person, scrounge up the money to contest the charge.