You probably don't need to go through the effort to become a 501(c)(3).

I've never seen it written down anywhere, but multiple IRS reps have told me that a good rule of thumb is whether or not you bring in $5000 or more each year (gross - i.e., everything, NOT just the amount after expenses). If it's less than $5000, there's not much need to formalize your status. More than $5000, you should be going through the process to set up a 501(c)(3).

You can still get an EIN, have a bank account, etc.

We are a PTA planning to dissolve and become PTO. We do not fundraise--only support. The only money we take in is for membership. Becoming a PTO--do we really need to be a 501cwhatever or can we get an EIN number/bank account and go ahead and start up?