Kyle,
Since it seems you dont want to or cant burn stumps (in many places you cant anymore as they burn for days) there are several possible avenues.
Have a tree co with a 2-3 man crew and in one day they should be able to cut and chip the 60-70 trees you have. Around here its $1500 a day for a crew of three with a
chipper. Have them leave the 10' 4-5" stuff for firewood and chip the rest.
Then rent a stump grinder and take out the stumps - I would estimate a medium sized one rents for about $250 a weekend - probably you can do 6-7 stumps an hour in the 6" range.
Second option is get a logger with a track skid steer with tree shears and a bunching head - it grabs the trunk and shears off (up to about 10-12"), then goes on to the next one grabbing 2-3-4 before laying them down nice and neat for the
chipper operation., The same guy probably has a
chipper so have him chip what you dont want. He/she would fell your 60-70 trees in 4-5 hours or less and lay them down.
Then either rent or have someone grind the stumps and spread the chips with your tractor. Around here operators with a small to medium
chipper are $350/500 a day and can probably grind 8-12 5" trees per hour (this includes operator and gas, etc) depending on the
chipper.
The dozer or excavator will remove a lot of dirt and roots, and make more of a mess plus disturb the existing tree roots so they will take some time to recover.
Now if you go the excavator route you will need to regrade, remove the roots and rocks, and probably more important rip up roots of the existing trees then dispose the stumps. For stumps - around here its $350-400 a 20 yard load, and $800 a 100 yard load (I paid $1700 for 200 yds of stump disposal last year). I would estimate you have about 30-40 yds of stumps.
Cost and time considered, I would have someone take down the trees chip the tops, leave the bottoms for firewood, then grind the stumps. I would say its $15-2000 to remove and chip the trees leaving you the firewood then $500 to grind the stumps and its all nearly done.
The least damage you do to the surrouding soil structure the better for the remaining trees - I have seen that first hand here with our 15-30" oaks and maples - they are struggling this year after ripping out the 30-36" pine tree butts around them - but they will survive and thrive with more sun.
My 2 C
Carl