X3 on the 2 liter engine. I have not owned a 2nd gen GV to date, but I would also recommend the 2 liter engine over the 2.5 V6. I've owned three 2nd gen Trackers, two with a manual transmission and one with the auto transmission. I have driven a ZR2 Tracker with the 2.5 and the auto transmission. Performance wise, (acceleration and additional "grunt") I can not say the 2.5 provides enough increase in performance to justify it over a 2 liter (to me). The extra fuel economy the 2 liter engine provides is a plus that just keeps on giving and when it comes to engine repairs such as timing chains, gears and water pump replacement, you will generally spend less money and time as well.
If you intend to modify the truck (with larger tires for example), there are diff gear sets available from other models that can help you off-set the loss of mechanical advantage. The 2nd gen body style and front drive train somewhat limits the modifications you can do with them without major modifications and expense, but they are still quite capable out of the box, their ride is much nicer and the extra room in a 4 door (for kiddies in your case) would work well.
But, as ZR2Tracker Joe mentioned, Chevy did make the early ZR2 models in a 2 door also. All of the above applies except the extra room of course. As with all of our older trucks, they are becoming difficult to find, but they are still out there to be had.