The new code will mean some overweight kids will miss out on a ride, with a weight limit of 51kg imposed.
It was drawn up by The Donkey Sanctuary, an organisation with 45 welfare officers which has taken more than 12,000 donkeys into its care since 1969.
The code has been endorsed by the British Equine Veterinary Association.
The code of practice is aimed at all local authorities with beach donkeys - which give rides to children - under their jurisdiction in the hope it will standardise levels of care and welfare throughout the UK.
The first copy was formally presented this week to the Mayor of Blackpool, which is home to the largest number of beach donkeys in the UK.
Blackpool has 200 of Britain's estimated 900 beach donkeys.
The code includes recommendations such as:
"We already see an excellent standard of care for many beach donkeys in the UK, including Blackpool," said Martin Taggart, the sanctuary's head of welfare.
"The code of practice will help to support local authorities to ensure all beach donkeys receive the same levels of care.
"The other purpose of the code is to provide a resource of advice and support to those working with beach donkeys or setting up new businesses. We are here to help in any way we can."
While the code is voluntary, owners risk prosecution under Britain's animal welfare laws for if they fail to respond to written orders to make improvement to standards of care.