Then corky 's suggestion is a very appropriate one:

And more on the dinosaur front would be the Natural History Museum, the Page Museum/La Brea Tar Pits, Cabazon Dinosaurs

The NHM and Page/Tar Pits are in Los Angeles while Cabazon is a good 2 hours of driving from Torrance.

WRT robots, a number of the South Bay high schools and middle schools have robot teams that compete in FIRST Robotics, both at the FRC and FTC levels. If of interest, there's also a few teams that do FLL (FIRST LEGO League (video: youtu.be/kkN08bDv9EI)) that's applicable to your 5 year old. Some of the local high school teams include 5124 (West Torrance), 294 (Beach Cities), 1197 (TorBots).

Going back to air and space, Space Shuttle Endeavour and multiple aircraft are located at the California Science Center near downtown. There are a plethora of other air museums across Southern California given the birthplaces of many companies in the region.

For pirates, there's the Pirates of the Caribbean ride as well as Tom Sawyer's Island at Disneyland. In an earlier time when the Pirates of Caribbean movies were dominant across the landscape, there were far more pirate related items that our middle kid had us going to around the area.

WRT construction equipment, there's plenty of work going on around the area but nothing specific I'd point to that you and your 5 year old could view and have any meaningful experience with.

And if he wants to try trains, then all of the suggestions and more made earlier still apply.

David

A trip through the U at LAX might be good for that. There's a lot of cool stuff going on with moving enormous concrete and steeel assemblies into place, though I think most of the time it's hard to see much of the equipment for doing it. Maybe from the top of one of the parking garages late at night. It's about an hour to get through the U and can be done on the way to somewhere else, like the science center or the beach.

Whatever you do, skip Disney. Unless you have fast pass, it just ends up being a very expensive walk.

Griffiths Park observatory is fun but can get crowded. The planetarium there is amazing, worth the price of admission.

I disagree about skipping Disney. Yes, it is expensive but just being in the park is a thrill everywhere you look especially for kids. Of course there won't be time to go on every attraction and there is some planning involved with getting a fast pass for some attractions and others you just wait in line for a little while.