Hey YG, here's a few quick points:
1) Donkeys really don't like dogs, especially dogs that are aggressive towards them, so you'll have to keep your dogs out of the donkey's paddock.
2) Donkeys are desert animals and very prone to getting overweight. They need far less feed than horses (but still need short feeding intervals to prevent colic). Once they get fat it is really difficult to reverse this. We have some donkeys that we got overweight nearly two years ago, and they are still slimming down - we use grazing muzzles whenever they free range on pasture - see donkey slimming thread in this part of the forum. A google search on "donkey feeding" will give you good information.
3) Fencing is the same as for horses. For small donkeys, maybe put a polybraid hot wire at a low level to stop them ducking under fences.
4) Train them similarly to a horse, but give them more time to think about things, especially if they are nervous about something. Trust is very important.
5) Hoof care is important - regular trims, and preventing seedy toe in wetter climates.
Horses and donkeys can get on great but introduce them with care like any new equine - start with adjoining yards/paddocks. Small donkeys can be bullied by horses at feed time. Separate supplementary feeding is always a good idea.
There are a few great websites attached to donkey sanctuaries in the UK and US with very helpful information on feeding, general care and training. Your google search should unearth these quickly.