To safely secure an area (in this case, your entire forest), you can have a miner dig around on the level underneath the surface using up-stairs as designations, then channel out the area above the up-stairs - the miner will channel out the tiles from below, thus securing an area without exposing any dwarfs. Then just send your woodcutters in, possibly also building a wall within your new moat to protect them from bolts and so on.
If you're dealing with ambushes, you might very well trap one inside your fort. In which case... fun is imminent!
As for tower-cap farms: Once you've uncovered the pool (or, incidentally, an underground river), ALL water that's subterrenean can generate tower-cap saplings on a tile. If you have another water source, it's best to dig out a large area near it, flood it (even 1/7 is enough), and drain it out. The muddied tiles will soon produce tower-cap saplings. Keep in mind it'll take a few years for the tower-caps to grow.
And animals: Just take like a male or female mule dog or something and use the pit function (i to designate a pit zone over an open space, then P to say what you want to shove in) and put them into a giant pit with a bridge at the top. They'll breed over a few years exponentially, and then you can pull the lever and they'll explode into bits for lots of bone when the bridge retracts.