Hi Rachel,
Don't know alot about the laser Large although I think Terra Nova quality is great , I have had the Laser and more lately the Voyager and they are both great, so assuming the size is right then I don't see why the ones you mention shouldn't be just as good !
There is extra cost linked to the Nallo 4 GT but they are quality , I have the Nallo 2 GT and that is great. Another good point is if you buy the fitted ground sheet it doesn't stop at the end of the sleeping area like most, it runs right though the tent which will help with the kids sitting in the for meals etc....... If the pegs are anything like the Nallo 2 then you may consider getting some others as once the ground gets soft they are of little use !
BTW I think Field and Trek are doing %age discounts on full priced items so you may save a bit :-)
No knowledge of the other sorry , but I am sure someone on here will help !
Cheers