In my situation....I have 3 kids and my wife is still a JW...I just use "Heavenly Father" or simply "Father" to begin my prayers and then address him as either or "God" in the main part of my prays.
For a certainty, "Jehovah" is incorrect. Check out this link: http://www.britannica.com/EBchecked/topic/651183/Yahweh
Basically it calls the actual name Jehovah, " the artificial name Jehovah (YeHoWaH)" and explains very well how it came into being.
That being said.....If that's the name you are comfy with...then use it. Afterall, the name/definition "Jehovah" is known to represent the one true God (I think anyways...could be my upbringing )... Anyways, I really dont think our Heavenly Father would be too upset either way.