(Not a landlord)
Probable reason for asking the kids names and ages. A family with primary school aged kids would most likely get chosen over a family with teenage kids. If any of the "kids" are actually aged 18 or over - run tenancy and credit checks on them as well. And if accepted their names also go on the tenancy agreement. Or property may have features that would make it unsafe for very young kids - EG a stream in the back yard.
Bond - a landlord can't apply for eviction due to unpaid rent until the rent is at least 3 weeks overdue. So even if there is no damage to the property, often 4 weeks bond won't be enough to cover overdue rent and water charges up to the tenancy ending. And landlords often won't accept bond transfers as they can't tell beforehand if the old landlord will definitely agree to release the bond on the old tenancy.
Employment status - Landlord probably doesn't want to rent to someone on a benefit. Unless that benefit is say the invalids benefit or another type that the tenant is unlikely to loose in the future. If employed - compare the rent to the applicant's income. Higher income means less likely to default on the rent because the car / fridge / TV / whatever broke down. Less likely to complain of dampness due to not running any heating whatsoever in the middle of winter.
Declined for no reason - Do you have any pets? Especially dogs. As that is a very common reason for being declined.