I really think you need to decide if you want to do Natsci or History. They are not very closely related subjects!
It's not that unusual for Natsci students to have 2 science A-levels and one arts A-level, but they might ask why you want to do a science degree if the majority of your A2s are in arts.
I don't know how common it is for history students to have 2 science A2s, but probably wouldn't matter as you have 3 arts subjects.
I'd advise you to take maths if you can't decide, as it is useful for any science and many careers eg jobs which take any degree often ask for 'nummerate graduates'.
In very rare cases (really a handful each year) students do get EE offers. but these are only given to outstanding students who will get AAA anyway (or better) to prevent them from being tempted to go elsewhere.
If you are looking for 'easy offers' you are applying to the wrong university. Even those who get slightly lower offers of AAB are usually predicted (and often obtain) AAA. In your case, if you were applying for Natsci without 3 sciences, you would probably get a higher offer. Not sure about History but I am sure a historian will post for you. Do you honestly think that it's all a lie and really Cambridge is really easy to get in to so some stranger on the internet will be able to tell you how to get a CCC offer?
You could always apply for Natsci then if you like you can switch to History and Philosophy of scicen for your part 2, to combine both your interests.