If you assign property to the trust, the property remains in the trust. After all, the TRUST owns the tax stamp, not you or your son.
Yes, trust laws vary state to state. Willmaker will account for this as it asks you where you are from.
The best thing about the software is the price. It's CHEAP compared to a lawyer, however, it is fairly limited. I purchased the software thinking it'd be a little more complex, as I wanted to do a trust with my father as a co-trustee. Not going to happen. Attorneys know the language and can explain it to you, but furthermore, the biggest advantage they offer is the ability to FORESEE POTENTIAL PROBLEMS.
I called a local lawyer about having an NFA trust done yesterday. Within 5 minutes, I'd been referred three times, ending up with the name and number of one of the NRA's council. Lots of attorney's won't touch them. One of the ones I spoke with didn't even know if it'd actually fly.
Needless to say, I'm still investigating.