I only helped my kids on one thing which I'll get to in a minute*. But as a matter of principle, all work was their own. Including not-so-neat handwriting, messy gluing, etc. And yes, many parents do quite a lot of work for their kids which I find abhorent. My sons both thanked me for NOT doing their work for them (later when they got older) because they recognized that it meant they had to learn not only to figure out the project themselves, but also to fend for themselves even when it was hard or time consuming.
I remember one science fair when my son was in elementary school where the mother of the first place winner was all excited, sing-songing, "We won! We won!" Hmmmm... We? Based on her jubilation, I'm guessing it was mostly she who did the work, as evidenced by the fact that her daughter was exhibiting much less enthusiasm. She didn't look like she cared one way or the other!
People think they are doing their kids a favor by doing the work for them but it is really a disservice and I'll give a couple of examples of experiences I've had where this was highlighted.
I used to be a Girl Scout leader (way back before I had kids) and at a multi-troop event, each troop was supposed to bring a girl-made troop banner which would be judged for prizes. I insisted my girls do the entire thing, from brainstorming for ideas to designing to figuring out supplies needed, to putting it together. It was 100% their project. The only thing we leaders did was provide transportation to the store and normal supervision.
When we got to the event, their banner stood out among the others as very girl-made. The other banners looked so professionally done and it was clear adults had helped. My girls were pretty dejected. "Look at how much better those look than ours!" I told them, yeah, but you did yours, they didn't. And no matter what happens, you can always be proud of your ideas and your hard work. Well, guess, what? My girls took first place. Thank you judges!!! Those girls worked hard and their work paid off!
Later, when my son was a cub scout, I was a leader for his den. In first year cub scouts, one parent always has to accompany their son to the meetings. One mother never let her son do anything. She did every project for him. All the other kids did their own thing but her son was just stuck sitting there watching mom do things. I tried to encourage her to let him try, to no avail. Not surprisingly, they dropped out of scouts fairly quickly. The reason? The son wasn't having fun, he was bored. Hmmmmm... really?
Back to your question, I do have one suggestion regarding the handwriting. If he doesn't like his handwriting, why not do the lettering on the computer? Does it have to be handwritten?
*The one thing I did help them with, in the end, was science fair projects. Only because they had to do them year after year and it got to the point where it was an exercise in futility as they were required to submit a project, it wasn't for a grade, and neither of them had any interest in the science fair. The whole science fair experience was just so negative for them and for the whole family really, that I just wanted it over with and so did they. It was the one exception to the rule. And believe me, my help was never going to get them a first place ribbon!