Most printers that I have used either work wireless or wired just not at the same time.  So you need to just put your Windows 7 computer on the wireless network.

Going to take a wild guess on your iPhones.  Your router probably has 2 networks, a 2.4gz and 5gz and they are named the same so you can't tell which network the iPhones are using.  Your printer is probably on the 2.4gz and the iPhones are on the 5gz network.  So turn off the 5gz on the router and connect the iPhones to the 2.4gz network and then try and print.

This is a copy and paste from Epsons website on how to name the networks so you can connect to the correct one.

Note: If you switch to a 5 GHz wireless router, set the router to operate in dual band (2.4 GHz and 5 GHz) mode. If your router uses a single network name (SSID) for both the 2.4 GHz and 5 GHz band, give each band its own network name (SSID) instead, such as Home Network 2.4 GHz and Home Network 5 GHz. See your router documentation for instructions.