Is there a way to click a single icon and open multiple application at once?

Yes, you can use Automator to create a workflow as an application, adding as many Launch Application actions as you wish. I'd also add a Pause action in between.

You can then drag the application from Finder onto the Dock if you wish.

Or you could use AppleScript in Script Editor, saved as an application, using as many tell application "appName" to launch statements. I'd also add a delay command in-between each.

Example AppleScript code:

property appNamesList : {"Chess", "Contacts", "Dictionary", "Font Book"}

repeat with appName in appNamesList
    tell application appName to launch
    delay 2
end repeat

If you did not have a bash script already, I'd tell you to do as per the answer given by user3439894.

But if your already have a bash script (say, named ~/open_apps.sh), you can create an Apple Script with the Script Editor application that says:

do shell script "~/open_apps.sh"

And then, Save the script to your Desktop, for instance, using Application as the file format, leaving unchecked the checkboxes for Show startup screen and Stay open after run handler.

After that, you can now launch that script (and hence your applications) by double clicking your new AppleScript application.

I do this by adding apps to the Login Items for my user in the Users & groups panel in System Settings.

When I log in they start.