When it comes to ambushes, walls are your best friend. You don't have to wall off the entire embark, just enough so that you:
- have 2 ways into the walled area on opposite sides
- have some sort of detection mechanism that the sneakies must get past
- said detection occurs far enough away for you to get civs to safety in time
I usually start with a very small walled area, then gradually spider-web my way outwards from that.
All civs who are not miners / hunters / woodcutters / nobles get shoved into militia squads with a minimum set of armor, crossbow, buckler, etc. I segregate my militia by gender / legendary status. So I'll end up with at least (4) militia squads as times goes on.
If you don't mind replacing watch-animals, build a 1x1 wall, build a ramp next to it, pasture the bird on top of the wall, remove the ramp. Leave a 1x1 stone or block stockpile next to the location so you can quickly rebuild the ramp. Granted, the poor beast will die every time goblin archers show up, but it's cheap and fast.
If you want to go with sacrificial animals, use a rope and a puppy. Expect many losses as the goblins uncloak to skewer the poor puppy. Or surround the puppy in cage traps to capture melee goblins.
As for war animals - never assign war animals. Or no more then 1 per dwarf. The other way to get war animals to follow dwarves is to take advantage of the fact that after training, the war animal will follow whatever dwarf trained it. Now that we can specify which dwarf trains which animal, this makes it much easier to train 20 dogs with 10 dwarves and end up with 2 dogs following each dwarf. (Not sure if they eventually bond, but it's less risky then actually assigning war animals to dwarves.)