<human>: Apologies for formatting/length, on mobile. Throwaway used for this topic before. 

I have known that my dad cheated on my mum 7 years ago for a couple of weeks now and I am really struggling with my reaction to it. 

I used to be a bit of a daddy's girl (not to minimise how close me and my mum are, tbh I just get on great with my parents) and so having to reconcile this image I had of my dad who was sometimes pretty bad at communicating but was a fundamentally good person and loved us all very much with the image I have now of someone who was willing to risk all of us for the sake of sex with some woman, enough times (or unprotected, I'm not sure which is worse) to produce a child. And then to lie about it to us for 7 years, until he retired and couldn't lie to us about going on business trips to go and visit her. 

I now feel like he is just a bit of a shit who never really cared enough about us to be honest or even to not do it in the first place. I feel a lot of resentment towards him for the way he treated my mother and what he put her through. However I still have a very strong feeling that he is still my dad and somehow I still don't want to hurt him, making me torn- I want him to know what he has made us feel, but also I don't want to hurt his feelings. 

This has come to a bit of a head as he wants to join me and my sister on a run we are doing in October and I just don't feel like I want him to be there, but he keeps asking what run it is. I want to reply something like "honestly, I do not feel ready for you to join us in this. While you have had 7 years to rationalise your decisions to yourself, it still feels like a very raw betrayal to me." But then just thinking about sending that to him makes me cry because it seems so cruel, despite me desperately not wanting him there and also wanting him to know that's how I feel.

Summarize the given text in a few sentences.
<bot>: my dad cheated on my mum some time ago and just told us, how do I cope with really disliking him right now warring with a lifetime of being a daddy's girl?