Shaylon could be OK. It's certainly going to fit in with all the two-syllable boys' names that have a long A in the first syllable and end in -n, a la Aiden and company. While many on NB prefer names that stand out more, I think there's something to be said for fitting in too. And I like how much meaning it has to you with the connection to your surname. You may read that it's a "variant" of Shea but I'd bet it's a modern, American variant, not a historical Irish variant. You might be OK with that, but don't think you're getting something you're not (i.e., don't assume the name has some tradition behind it).
At the same time, I have some real reservations you may want to chew on:
1) Say it out loud. It sounds A LOT like Jaylen. Jaylen is such a popular name for boys right now, I feel like there would be lots of clarification needed.
2) While it gets points for being easy to pronounce from reading it, it's not at all clear how to spell it. He'll be spelling it a lot. But that's true for a lot of other names to be fair.
3) Shayla, I think, is more familiar for girls than Shaylon for boys. I think a lot of people may hear Shayla when they first hear this name.
While it's worth thinking about, I think Shea or Shane or even those Irish names that started it all, Aidan/Aiden could be far preferable. What was your maiden name, if you're comfortable sharing it?
Gotchya. Wow, yeah, that is a shame that it is so close to Shannon, because it has real potential.
What do you think of Shane? To me it's even closer to your name than Shaylon.
If you google the name Shaylon you get about half women and half men coming up with the name.
This site is also interesting about Shanahan
It suggests the name is derived from the same root as Sean. What do you think of Sean?
Gotchya. That's a reasonable line in the sand to draw, although with Shane at 215 and falling I doubt there are that many more baby boy Shanes born every year than whatever name is at 301.
Nash comes to mind. All the letters are in your surname : D, and it fits in with Cash and Dashiell and Asher being popular. I think it has good flow with your middle name pick. In general I think one-syllable names are going to work well for you.
Shai is cool but I'd have reservations about calling my kid Shy. Like, if he really is....that's going to be hard.
Shea isn't even in the top 1000 (for either gender) and I think is less problematic.
I did a little more digging on Shanahan. Other websites give the meaning as "wise" as well as "old", and another Irish name that means "wise" is Redmond, also given with variants Reamon, Reamonn, and Reamonnn. This is the Irish take on Raymond, and then I think when it got put back into English, Redmond happened. I kind of like it.