Greetings from Down Under!

My family and I (wife and 2 x 11 year olds) are flying to NYC mid May and then after catching up with family onward to FL (St Petersburg / Clearwater area) for more family catch ups before heading to Dallas for the flight back home to Oz.

Rather than fly these sectors and miss the opportunity to see some of the US (the kids and I have never been and over 30 years for the wife), I had the crazy notion of driving it! (cue National Lampoon music).

Now I have planted the seed, the wife is asking me questions which thankfully, Google led me here so I'm hoping you might be able to help.

1) How long (excluding sightseeing) should it take to drive from NYC to FL
2) Which is the best (most scenic) way to go? I've read the I-95 is just a city bypass with not much in the way of scenery.
3) Based on the above, any 'must see' sights, touristy things along the way
4) From FL to TX I'm assuming the I-75 / I-10 / I-45 is the best way
5) If the above is true, more 'must see' sights etc along the way

We'll have roughly 3 weeks in total from the time we leave NY to when we have to get to DFW so maybe a week on the road for each leg - No all nighters or land speed record attempts required.

Any advice you can give would be greatly appreciated so the wife can either yay or nay the idea.

Thanks
Scott