I recommend you get experience with handling and working with donkeys before you own them yourself. They do require handling and training to ensure they are safe and respectful especially if you get them as yearlings.
You also need to make sure your dogs will be ok with them as dogs who constantly bark and freak out at them will stress them and stressed out donkeys can be very dangerous if you don't know what you are doing.
You can't have donkeys and chickens and ducks housed in the same area/field without fencing. This is because some donkeys hate chickens/ducks and will kill them. The same goes for dogs.
Also, make sure you are aware of the costs associated with donkeys. They are very expensive. Hay costs a lot depending on the cut and your location along with environmental factors that may have helped or hurt a harvest. You also have vet bills. Vet bills are very expensive. They need their teeth floated every year which will add up with multiple donkeys all having to go under some anesthesia, will be pricey. You also need to factor in emergency vet bills if they colic or go lame.