Welcome @mlg!
My son is only 4 (diagnosed at 2 yo), but I’m having difficulty waking up myself now to alerts. This thread has some great recommendations for how you can make alerts louder, etc., so that your son can hear the alerts.
I am planning on purchasing the Sonic Alert System, because it allows me to have other external sources of light/sound that will enable me to wake up. You may want to consider investing in such a device!
Again, Welcome!