My wife and I were in a situation similar to yours. We were spending $81/month for two phones on AT&T. In January '09, we switched to Page Plus and we have saved hundreds of dollars. I am very happy with Page Plus.
You do not have to buy a phone from Page Plus. You can use most Verizon phones. You can find good phones on Ebay, and for what you are describing, you can probably find phones for less than $25/each. Keep in mind, 4G phones and Verizon phones that were originally sold for their "Inpulse" (i.e. prepaid) service will not work on Page Plus.
Since you only need 200 minutes per month, you should be able to get by for an average of about $5 each for voice, plus 5 cents for each text that you send or receive. When you purchase $80 of airtime, it will give you 2000 minutes. The minutes will be good for one year and they will roll over if you add at least $10 at the end of the year. Page Plus will also debit 50 cents from your account on the 25th of each month. I would recommend reading all of the details on the Page Plus website.
I have never had any trouble with SPAM on my Page Plus phone, so I don't know what to tell you about that.
You are going to save a great deal of money by switching from AT&T to Page Plus. You might want to do the math and see if your savings will warrant cancelling your AT&T account early and paying their ETF