Yes, you can add OPEN as an Action, however, this would not be ideal in my opinion. This way would be more time consuming... And also, the action will attempt to open a file that you opened before. I don't think you can assign the action to open random files...
A better idea would be to select multiple files and open them all at once. And then record an action for as follows...
1. Press CTRL+O to navigate to a folder where all the images you want to change the size is located and hold down the CTRL button and select and then press Open.
2. You will notice that all the files will open up on the desktop in an orderly manner. They will all be cascaded. Open up the Actions windows and then press the blank document icon to create a new action and press RECORD.
3. Resize the first image and resize it to desired size and then click on the image just behind it and resize it. Now that you've created an action to be played, you can STOP the action recording.
4. Now just click the PLAY button or a function button if you assigned one as fast as your little fingers can click and you'll be done resizing images in no time..
