Most of the free solutions will do the job, however many of them don't offer free support or their support is offshore and email only.
Microkeeper is a payroll and STP solution that's free for 1 admin with 1 employee, and paid plans are very competitive too.
Microkeeper has phone and email support in Australia.
A small account, with a handful of staff, can usually be up and running in 10 minutes.
All the free options are self service, I would suggest giving them all a go to see which one is the best fit for your customers.