do I need to leave those pins unused (or maybe connect a keyboard to it - while programming I won't press any buttons
somewhere in this discussion there is someone that modified my NoTouch for The P89c51Rx2 to work on Atmel.

If you can not find it, have a look at NoTouch (and the emergency exit) at my user page and with a Philips datasheet together with an Atmel datasheet the needed modifications should be obvious. Of course, if you buy the Philips version instead, you can use NoTouch as is.

Erik