As salamu alaykum,
I am not an Islamic Scholar but I think you are correct in handling the situation as you are. You are teaching your son about Allah’s love, mercy and protection at an age appropriate level. This is most important and fundamental for little children to learn, that Allah SWT is Al-Muhaymin, Ar-Rahman; Ar-Rahim. As he grows older he will be able to cognitively process the deeper concepts of Islam, but for now, he is blessed to be learning the basics as many parents do not start teaching their children to be thankful to Allah, or to turn to Him for protection until they are much older. You are doing a wonderful job mash’Allah! Insha’Allah you might also want to recite ayat al-kursi to your son as the Prophet Mohammad (PBUH) told us of it’s protective powers from evil (bad dreams) when recited. By reading this ayat to your son every night, he will begin to learn the words and later the meaning and soon recitation of it will insha’Allah come easy for him. Additionally, it will be something he will get used to reciting, which will be a blessing and protection for him as well. May Allah bless you sister for your efforts in teaching your son about Allah SWT.