I assume your Kiosk database is at centarlised place as you mentioned Kiosk terminals to be Thick client on Windows 7.
I will recommend to use 3 Tier Architecture as it provides following advantages: 1. CRUD operations can be made Database type and location agnostics. 2. Database Security can be taken care easily at Web sevrivces layer using https - SSL connection. 3. Methods that your Kiosk class uses to execute procedures will return values from within the functions such as ValidateUSers, ValidateCard etc.