It sounds like you may have a plan, but have you considered a roller-chopper for this job?
They have been used to good effect here in reclaiming pasture overgrown with small cedar and mequite. Basically, a large roling steel drum with cuttings edges that you pull over the trees...similar to the way you would plow a field. This breaks them down and creates a dense, dying amount of foliage close to the ground which then is very easily burned in controlled burns. After the burn, you go in with a dozer and rake the left over material, plow, and re-seed.
Now, from your pic, these pines look to be about 10' or so...? I've a D-6D pulling a roller chopper work over a pasture full of cab-high cedars with relative ease...and do it much quicker than pure grubbing. Maybe you should check with an experienced clearing contractor about this option and see what he thinks.