Quite simply you have far to many gadgets trying to connect to the internet at once. You will need to limit connections at the same time. Certainly get a decent router as this will help, hopefully in the future speed and will improve to rural locations.
Your sons will need to understand that for the time being they will not be able to hog your broadband connection with gaming whilst others need it for other reasons. But surely you do not need every gadget connected or rather using the internet all the time.