Visual FoxPro 9.0 SP2 is an ideal fit for this, because the database engine, reporting tool and so on are all first-class and integrated into the product. It can easily handle huge databases and many concurrent users.
The only problem of course is that it is nearing official end-of-life, will never be 64-bit, everyone thinks it's dead because that's what everyone says on Google and so on.
MS Access would also fit the bill except I would have question marks over the richness of user interface available there, and scalability.
You could also consider RealBasic perhaps ...
