Access Wifi services without losing 3G

The project is to develop a very basic Android app which will establish a connection to a pre-defined wireless access point and allow access to local web content on that LAN without the mobile phone dropping the 3G connection. As a general rule when a Wifi connection is made by an Android device, the 3G data interface is torn down and the phone's default route becomes via the Wifi connection. In the case of this application we require the 3G interface to remain connected and able to service normal internet activity, that is to remain the default route and only data within the same LAN accessible via the Wifi Connection. The wireless access point will be running DHCP configured by me so special case Dhcp configurations may be possible. The solution is to be delivered as an installable .apk as well as providing the source code for the application so that we can then add functionality as needed in-house or via a broader project here. Please note that the devices that the application will run on are not owned by us so options which require rooting the device are not acceptable. Please check for yourself that your proposed solution will work as the first payment milestone will be 75% payment after delivery of a working example .apk to show the solution works and then final payment after delivery of the source code developed. App should be compatible with at least API8.