I bought my 2nd kit some weeks ago and learned a few things.
High Grades are pretty easy, for sure, but that usually ends up a blessing (or a curse, from your wallet's point of view). Since it doesn't take too long to build one, you can knock out quite a few without much issue, which means you can amass a decent collection of kits to pose together (and like you said, a Gundam just looks great fighting multiple grunts). Of course, this also means you can start running into cost or space issues if you get carried away...
As
@00R-Gundam said, there's really nothing all that different between the simplest and the most complex kits when you really get right down to it. You're always going to be cutting out parts, cleaning them up, and putting them together. The only real difference is the amount of time you end up investing in a single kit. If you want to stretch how long you spend on a kit, consider learning how to detail. Panel lining is a great place to start; it's cheap and easy, but it really helps make your kits pop.
Bandai's plastic is pretty sturdy, I've never had issues pulling pieces apart and putting them back together. Hell, most people will do a dry build first before they begin detailing so that they can see how everything fits. I imagine that they'll hold up to more disassemblies than you're likely to do, as long as you aren't doing something stupid like trying to force a part to bend in a way it wasn't meant to.
I'd suggest trying out a Master Grade to see how you like that particular scale. They're 1/100 scale so they're larger than the kits you've built so far, but they have a complete inner frame like Real Grades. That might satisfy your desire for more complex kits without running into the issues that a lot of the early RGs have with their inner frames.
And definitely look into getting an Entry Grade for your son to put together. They're so simple, they don't even require tools, you can just pop the parts off the runners with your hands. Despite this, they're sturdy and quite posable. I think it's great that you want to include him in your builds, but if you want him to have something he can build on his own too, you can't go wrong with an EG.
I just finished up the RG RX-78-3, and I can confirm that all the complaints are valid. It's based on the original RX-78-2 kit, the very first RG, and it was quite a pain to build. The pieces didn't always want to stick together, parts kept wanting to fall out, the hands don't like holding onto anything, and even doing a simple pose was such a challenge. The shield in particular doesn't really want to stick onto the arm, and you basically have to hold it up with the hand to keep it from falling out. It didn't help that I lost a piece while trying to put the arms on, and it took a couple days to finally track it down and reattach it.
So why'd I get it knowing the issues? Well, for one, I still wanted to have the experience of building the original before I got the 2.0, so I'd have something to compare it to. I could have gotten the RX-78-2, but I'm not overly fond of getting the same mobile suit in the same size multiple times. Since the G-3 is virtually identical, I could just build it instead and have something different. For another, despite the problems, the end result looks fantastic. I think it's the best looking version of the G-3 in 1/144 scale, it has a muted color palette that ends up looking really nice.
And finally, it's part of my long-term project to complete the RX-78 line in 1/144 scale, and I now have three out of seven done. Waiting for the G04 and G05 to show up on P-Bandai again (stupidly waited too long last year), and I'll grab the 2.0 RG at some point. Still have to decide what to do about the RX-78-1 since it doesn't have an official 1/144 kit yet (or at least one that didn't come out forty years ago).
But honestly, if you're looking for a G-3 kit, wait for Bandai to inevitably release a RG 2.0 version of it. Pretty much every RX-78-2 kit will eventually get a G-3 recolor, and based on what I've heard, the 2.0 is a stellar kit to build and pose.
One more thing: it's gunpla announcement time again; they'll be talking about kits coming out in Q3 of this year, and we should get word of the specifics later tonight. Place your bets! I'm almost certain we'll start seeing more of the GQuuuuuuX line announced at a minimum. Hoping to see some Gundam X announcements ahead of the 30th anniversary next year, and keeping my fingers crossed for a RG Master Gundam.
