Well, the first episode of Astro Boy usually involves the death of the child Astro's based on. Although, as long as you don't show him that first episode, everything else should be fine. And if you can track down the 2003 Astro Boy anime, that'd be a fun watch for him.
I'm assuming that you're watching all these dubbed? He's probably a little young for sub-only shows? So, something like GaoGaiGar or Shinkalion or Kotetsushin Jeeg is probably out.
Since he seems to like robots, I'd suggest Gundam Build Fighters. That's a lighter show without any death in it. Although, I'm not sure if the the dub is actually worth watching or not.
G Gundam is also a possibility. It's a little more intense, but still not as serious or dire as other Gundam shows.
Medabots I think would be right up his alley, if you can track it down.
Zoids. All the Zoids series. I think he'd dig that.
Escaflowne feels like it could be a maybe? Or the Giant Robo OVA? Or Gunbuster? Maybe when he's a little older? I'm not sure.
SSSS Gridman feels like another maybe. Along with something like Saint Seiya/Knights of the Zodiac.
Cardcaptor Sakura or Sailor Moon are good, but he might think they're too girly.
Slayers, on the other hand, might have enough action and comedy to keep him interested. It might also be worth trying Little Witch Academia.
Maybe Megaman NT Warrior? It might be a little confusing for him since those games are getting a little old now, but he might dig the anime.
Voltron seems like kind of a no brainer.
And as long as you've got him watching older anime, you might as well try Gatchaman/Battle of the Planets.
Zatch Bell I think would be fun.
Same for something like Rave Master.
Or even Fairy Tail.
Or Black Clover.
Or Dr Stone.
Or InuYasha.
Or Ronin Warriors.
Oban Star Racers might be fun for a watch.
I think the Mysterious Cities of Gold would be a pretty fun watch, again, if you can track it down.
The english dub of the first season of Duel Masters might be kind of a fun watch. It might one day prepare him for the english dub of Ghost Stories, which he should not watch yet.
Ultimate Muscle might be fun.
Shaman King might be worth a watch.
I know there's a dub for Doraemon. I'm not sure how available it actually is, currently. But it does exist, and it can be a lot of fun.
One Piece would probably be fine. And you'd certainly have plenty to watch. It might be too long, though.
Yu-Gi-Oh. As long as you don't start him with the darker "Season Zero", I think he could probably handle that.
Dragon Ball and Dragon Ball Z are a maybe. Sure, there can be a lot of death, but it's all treated so causally that he might not even mind.
If he likes Pokemon, you could show him some of the other monster collecting or toy based anime. Like Digimon, or Monster Rancher. Or the original Beyblade or Bakugan.
Then there's stuff like Daigunder, or Dinozaurs, or Fighting Foodons, or Mon Colle Knights, or Flint the Time Detective, which I have NO idea how you'd track down.
...That's probably too much, but you should have options, now. I'll admit, some of these are right on the edge of what he might be prepared for. Some of the action shows might be a little too violent for him, or he might love them to bits. I did try to pick ones from the "lighter" side of action, though. Most of these could air on Saturday mornings without much issue, I think.