I've played all three, and I like SH4 the best, but I like the US Fleetboats, not that the German Uboats weren't fine machines, but it feels more "natural" for me to be in a US boat. As for mods, Fall of the Rising Sun Ultimate (FotRSU) is what a group of us are working on now. It's at beta version 0.63, about to progress to 0.something-or-other, with some neat changes coming. The mod is based upon TMO 1.7, but has many additional ships and planes (and subs) added mostly by the AOTD_MadMax team, the authors of the original version, but with contributions from others. I had always liked Fall of the Rising Sun (FotRS) from years ago, but the Ultimate edition has many improvements. Even though it is a beta version, gameplay is more stable than several other mods. Plans are to have a mod number scheme to help designate which mods are known-compatible and could work with FotRSU. No other mod has yet done that. The player will also be able to set their own difficulty level of several aspects of the game. This has not been implemented yet. I think you'd like it, and like most mods, you can choose how much you want to have to do in the Gameplay settings menu, even to the point of not seeing the target on the navigation map. I can't hit a barn like that yet...
- course, I won't mention how inaccurate I am with all the bells and whistles turned on, either...
FOTRS Ultimate Project - shameless plug from a very opinionated author, of course...
It sounds like you might not have a whole lot of time though to mess around with things, and want to get right into as-realistic-as-possible play with a "finished" product. With that in mind, you might find that you'd like Bleiente's mix of TMO, RSRDC and Optical Targeting Correction (which you wouldn't have to use), which is an add-in mod from CapnScurvy (on the FotRSU team), in which he included a difficulty tweak called "Tokko's Revenge". Bleiente put it all together in
Ralles RealModPack for TMO_RSRDC_OTC. A slightly more complicated install, due to the options.
Of course, you can't go wrong with
Trigger Maru Overhauled (TMO) v2.5. Of note, there is a Small Patch for TMO, not from the author Ducimus, but it does fix issues with the Tench class boat. Also, be aware that TMO activated with JSGME will delete two German flag files, which do not get restored when the mod is de-activate. Usually, not too much of a problem.
As to getting the kids to watch it on the screen as you play it? Well... my boys think it's "boring"... takes too long for things to develop and all. They do like the explosions though, even if it is ~my~ boat that's blowing up... Here's another thought, buy a 2nd copy for a 2nd computer, have both on a network, and put your boys on the one computer, you on the other. Just take it easy on them for a while though, and don't do what I did, to where I now have to twist their arms to get them to play...
Edit: I neglected to mention
JonesSoft Generic Mod Enabler, which is the tool to use to enable the mods above... the user's manual is here:
http://www.subsim.com/radioroom/down...o=file&id=3814
if it's not in the JSGME download...