I had an old child's apron, an Ebay purchase from long ago, which was about the right size, and which we used as a template.
We went through the tedious stuff like cutting out, and ironing seams. I showed him the old apron, and how & why the seams were double folded. I pointed out how even they were, and said that that was what we were going to try and do. I made him help me fold and pin.
He practised sewing on some scraps, and then he sewed the straight seams, including the first sewing in of the tapes. We checked, checked, checked at every step. I sewed the curves for him, and he did the top and bottom.
It looked good so far.
We did a fitting to adjust the neck tapes and the waist tapes, and agreed that we'd g for long waist tapes he could do like chefs do, cross over at the back and tie at the front/side. We then discussed the size and position of the pocket. There were two dinos in particular that he wanted included, so we had to work out how much of them we could get in to the space available. I cut the fabric, and got him to iron the hems. He then sewed the hems down - a little wonky, but not bad - and then I pinned the pocket to the apron, and he sewed it to the apron. Again some of the stitching was a little wonky, so I asked him what he thought we could do to disguise it. He suggested adding some decorative stitching, so he tried a few and then picked a decorative stitch to sew- - in a coordinating colour.
I reinforced the tapes for him, and the pocket corners. I also put Velcro on the neck tapes.
I then suggested he might like to embroider his initials on it. We looked through the fonts I had, and he picked one he liked. I showed him the sizes, and then we did stitched them out on the embroidery machine, so he could see what they looked like. This also meant we could use the scrap to accurately decide where to position them on the apron. We then hooped up the apron, and did them for real.
The finished item is really impressive! He's done a great job.
He still wasn't finished. Did we have time to make ginger biscuits? We whipped up a batch, and used the fabulous Oxo Cookie Press. Then dinner. Then a bit of robotics with grandad. Then 1 hour's TV, during which time we discussed Sherlock Holmes's characteristics and Johnny Lee Millers portrayal in particular. And then bed. I was shattered, so I went too!