Social worker coming to visit my dad and I?

Tomorrow afternoon tues 3-29-11 a social worker is coming to visit with my dad and I because supposedly the bank has called saying I have been stealing from my dad. He is 76yrs old and my mom ped away 5yrs ago so he does what he wants with his money. He gives me authorization to use his credit card because I dont have one and I use his, however Ipay for any purchases I may have made unless he says otherwise..He knows this because he gets his statement once amonth and hes fine with this. Hes upset that he going to be questioned on how he wants to spend his money and her (social worker) accusing me of basically theft. My question is do we keep her outside and how do we answer her questions so shes satisfied that Im not doing anything wrong. My father doesnt want her in his home. We have a nice porch. What are your recomendations...please help