Installing several applications at once from Inno Setup
An Inno Setup can include other setups and extract/run them on any condition, including dependancies (not) existing, user prompts and [Components]/[Tasks].
You can use a normal [Files] entry to extract it into {tmp} and a [Run] entry to run it.
If the other setups are external to the Inno setup, skip the [Files] entry and use {src}\BlahSetup.exe for the [Run] entry.