If your kids are grown, maybe you could just get by with a phone card or email. The cell phone might be unnecessary if you don't need for them to have a way to contact YOU in an emergency.
Or maybe your phone company can unlock your cell phone unless you have a CDMA phone as I do (common with phones on Sprint or Verizon, but you might have a global ready phone). If you have a tri-band or quad-band phone, you're in luck.
I looked at this same package from Telestial too, but the per minute rates were so exorbitant that I bought an unlocked phone elsewhere and plan to buy a local SIM card when I arrive. Actually, though, I also bought a T-Mobile SIM from their website ($7.50 with tax and free shipping) that comes with 10 minutes in the US (and can be topped up), so I could use the phone in the US too while in transit and not drag my useless regular phone around Europe for 4 weeks.
I did look at unlocked phones on eBay, but I decided to buy a new unlocked Razr directly from Amazon for $64 (so the battery would be new, and I could return it if it didn't work). I need the phone for emergency use in the country, though, so I was willing to pay extra for this.
If you do go with the Telestial phone, you can still buy a SIM card locally. And you can use this coupon code to get 15% off your purchase from Telestial: FROMMERS01. I found it on retailmenot.com and it works.