I am Canadian citizen and wish to stay in US for 12yrs continuous to support my 2 children's(US Citizen) education. I do have employment offer in engineering trade in US which qualifies for bothTN and H1B.
What would be the best way for this continuous stay with minimum hassle -TN to H1B to TN, TN-TN-H1B,H1B-TN-TN.....and I donot want to apply US PR as I will be back in Canada after kids graduate..
Any option not involving starting on H-1B will potentially work. You can't start an H-1B until Oct 2014 due to cap availability unless you are cap exempt.
The risks of the TN are that there is some risk of denial if you stay in TN status for too long--although there is no hard and fast time limit. Plus IMHO it is a more limiting status than H-1B. There's no hard and fast rule saying that you couldn't just get four consecutive three year TN's. But if you've been in exactly the same job for 9 years, by the time of your final renewal USCIS/CBP may begin to question whether the arrangement is truly temporary.
The biggest problem with the H-1B these days is that there is a level of randomness to it. One needs to apply in early April for a position that will start in October--and in recent years the cap has been exceeded almost immediately when applications selected at random for approval/rejection.
So you have to have some flexibility in your strategy because there is no guarantee that you will get an H-1B any given year.
If it were me, I'd start with a TN and then apply for an H-1B every year--beginning next year--until I got it. In parallel I'd start GC processing. There's absolutely no downside to having a GC (except in the very unlikely event that you are male, under 26, and the draft is reinstated). If things go as planned you can give it up almost as easily as giving up a TN or H-1B if you do end up going back to Canada as planned.
The GC application has the additional advantage that it allows your H-1B to be renewed beyond 6 years--even if your visa number is not yet current. If you know you are going to be in the US for the next 12 years I really see no reason not to apply for a GC.
The primary risk of the H-1B is that it has become somewhat random who gets an H-1B.