Dear @Kevin . Thank you for your question! It does sound like a troubling time for you; I do hope that everything remains well for you and your family especially with the number of cases in America. 

I would say that it is appropriate for you to sleep in a spare bedroom. Beyond that ensure to always use gloves when you are working, wash your hands thoroughly during working hours as well as before you leave for home and before you enter your house. It would not be out of the question to even shower before going home. As it has been found that a small proportion of people can remain asymptomatic with the virus and still spread it around, it would not be out of the question to stay somewhere else entirely. It would be best to limit your contact with your wife and especially your younger child. Though the number of serious cases amongst children have not been very high, they are at higher risk given their physiological state (poorer reserves) compared to adults.  

These measures are necessary as COVID tends to linger on surfaces as they are unable to remain suspended in the air. Hence it is more likely for you to get it from touching an "infected surface" followed by touching your face or eyes/eating/sharing food or drinks with colleagues. I hope your company has thoroughly disinfected the premises as well. 

Wishing you and your family all the best!