Your plan will work and you have several choices.
Make your USB dongle the highest priority connection and allow it to obtain an IP address automatically as you do now. To change adapter priority go into network control panel, click on change adapter settings, hit the alt key to get the menu across the top, select advanced and then advanced settings, move your wireless to the top.
In the network control panel right click the Local Area Connection, select properties, double click on Internet Protocol Version 4 to bring up its properties, then give it a static address after you have assigned it that address in the router either static or reserved dynamic.
You should then be able to get on the Internet, and if you set the permissions and sharing (you must use both the sharing and security tabs to allow sharing) your wired network can share files.
If you want all the devices to have Internet access you can either use Internet Connection Sharing or bridge the wired and wireless USB adapters -- just be aware that the bridge can be a security issue.