UK standard visitor visa application for multiple visitors

I'm new to this forum and joined because I cannot find the information I want anywhere.

I am British by birth and my wife of 8 years is Thai. She has been living and working in the UK now for 7 years on ILR. We would like her Thai daughter and two children aged 5 & 6 to visit us for a month on what I believe is now a Standard Visitor visa. Myself or both of us will naturally sponsor the visit.

The application form however is geared for a single adult application and I cannot find any facility in the application process to include two children on the visa. It is inconceivable to expect two young Thai children to make their own visa applications so there must be a way of applying for all three persons in the same application. Can anyone give me a brief outline of what we need to do? Any help would be much appreciated.

Thanks