IOS doesn’t allow scripting with any browser, so that part is true. However, if you don’t mind using an app, Tsurukame provides a lot of the functionality of several scripts so you may want to give it a try.
The best way to use vacation mode is listed in the Ultimate Guide:
The gist is to stop lessons about a week or two beforehand to clear out your apprentice queue. Then you’ll only have Guru and above items when you start vacation. That provides a much better way to work with the SRS.