Hey, William.  Sounds like you are having fun with it!  Regarding this part: "why can’t I write stuff like this? It’s just a blues scale!!"

In my experience the reason is rhythm.  Specifically rhythmic phrasing.  

It's relatively straightforward to see the notes on the fretboard, to understand the patterns various scales make.  Pentatonic minor & the blues scale are basic and straightforward.  But rhythm is more abstract.  Unless you are reading notation you can't see it.  And even then it's still just a graphic representation.  It's like directions on a map versus actually driving the terrain in real time.  

Some players have a more immediate and intuitive sense of rhythm.  Others have to work at it more to develop it.  But it is something that can be learned and developed.

The first step is to start to think explicitly about rhythmic phrasing.

Most riffs and melodies are made from combinations of 2 to 4 measure phrases with some similarity and variety.  Think of something like the Smoke On The Water riff.  Count it out.  It's basically a simple scale fragment played ascending on downbeats for the first measure, then on the second measure the same notes go up again with a little variation but this time on the upbeats until the end of the measure when the last one lands on the third downbeat again.  Then for the next 2 measures the phrase starts the same but with a different ending landing back on the root on an upbeat.  The repetition with just a little variation, the variations in rhythms is what makes it catchy.

The point here is to think about riffs that are catchy or that you like and count the rhythmic phrasing.  The notes are only one element.  The rhythm is what gives the notes motion, as a musical line happens in time.

It can help to do exercises in which you play a scale trying to make a 1 or 2 measure phrase that sounds good on repeating or looping it.  Don't use the same rhythmic note value the whole time.   Use a combination of quarter notes and eighth notes.  Try to include a variety of notes on the downbeat then the upbeat.  Change the last note of the phrase with second time through.  Aim for simplicity.  Don't try to play too many notes or use the whole scale.  You're trying to make a phrase you might hum or sing, not just play scale notes.

This is the same process that can work to develop a lead guitar vocabulary.  You are learning a language of things to say in a specified time unit.

Keep enjoying what you can do, especially with your kid.  That's the best.  Hope some of that helps!