Welcome!
How much time do you get to spend with the kids? Do you have non-JW relatives?
I'm not a parent, but I was an elder enough to see how these things can go sometimes. My first suggestion would be to get to know what's going on with the kids. Help them to feel really comfortable and relaxed around you.
They're probably getting programmed to be uptight and defensive around you, their dfd dad. And they're too young to effectively become independent... when they get to their teens, that will come out! Make sure they understand that you love them and will listen to whatever is in their hearts.
As I remember growing up in WTland, I got plenty of lecturing on what to say, think, and do from my parents and all the KH sheeples. I didn't need someone to ramp up the internal conflict of proJW/antiJW rhetoric. I needed an adult that really listened and cared about me... without all the WT crap.
While they're young, it can be hard to listen to and understand their thoughts as kids, but it sets the groundwork for a solid future relationship.
But that's just the opinion of an exJW ex-elder.