If you've got a nightspinner conversion kit I'd definitely put that on one of your tanks. I know the kit you're talking about and it looks sweet, so go for it. Rules wise, I haven't used nightspinners before, but I have friends that play eldar that swear by it over fire prisms, so that counts for something.
And from the sound of it, it seems like you haven't taken the dive into the current edition's rules. But as mentioned above, if you take 3 falcons together they all gain a pretty powerful special rule.
That special rule allows all of them to deep strike without scattering, and if you combine that with squads of fire dragons mounted in your falcons...I think you see where I'm going with this one