If you follow basic sanitation rules, you and the kids will be fine.
*Always wash your hands/arms (& exposed parts) with soap and warm water after handling the birds. This is especially true before eating.
*Maintain clean living conditions for the birds (coop/pen and run) - this is for the protection of both
Everyone is exposed to almost all the normal types of bacteria - you and the ducks. Just minimize exposure by keeping clean... there are no risks beyond those of normally playing outside. Be aware that some types of flu virus can spread between birds and people (usually people giving it to birds) so if you get sick try to minimize handling.
Check out David Holderread's Book - Storey's Guide to Raising Ducks. There is a chapter on biosafety in the book.
Cheers,