Scattering of ashes... am I being selfish?

[Hamsternautss]

My dad died in extremely tragic circumstances nearly 2 months ago resulting in his life support being removed, he was cremated a month ago. He was only 62 and I was his only daughter.

My dad used to take me on holiday almost every year to a specific place growing up. We did go to other places but this place was his absolute favourite place in the world. When he died there was no question in my mind where I would scatter his ashes.

Fast forward a few weeks since his funeral and his foster brother called me today and asked me to let him know when I will be scattering his ashes at this place as he would like to come too. He caught me on the spot and I just said I'd be in touch.

My dad and his foster brother were not especially close, lots of years with no contact and very sporadic when there was. But my dad did think a lot of him and they had a mutual respect for each other. I've met him twice in my life, one time including the funeral.

He has completely caught me off guard with this one as I had envisioned doing the scattering on my own as that how it always was with dad growing up; just me and him. No one else has requested to come along to scatter, not even his blood brothers one of which who he was closest to.

I really wanted this final moment with what's left of him by myself to say what I wanted to say and now I feel like I'm going to have to share it with someone I hardly know. I won't be able to say everything I want or cry how I need to. He put me on the spot and I didn't have a clue to say how i was just hoping to do it alone.

I feel selfish for wanting to have this moment for my own and now I don't know how to back track without really offending him. We are on very different wavelengths and he is very religious. I likely will probably never see him again otherwise but I wouldn't know how to backtrack. He didn't even ask if he could come, just wanted me to tell him when. Aibu??

@Hamsternautss

Sorry I posted too soon and my last paragraph causes a contradiction.
What I was aiming to say was that in our situation, my brother and I had a close relationship with my Dad and having been told that we'd be involved in 'everything', we have been cut out due to vindictiveness. Our stepmother said that she didn't want Dad in the family plot but then refused to sort out a new one for just them despite us agreeing with her - it's just utter viciousness on her part.
Your situation is nothing like ours as had we not been close to our Dad then we wouldn't have any complaint. We helped with funeral arrangements and helped pay for it all so we didn't leave our stepmother dealing with it alone. She then told everyone that it had been hard doing it all alone -at the wake! If we'd left her to it then she'd have every right to complain and to do as she liked but we didn't and my brother was particularly affected by it. Your situation is nothing like mine.

Your Dad's foster brother hasn't done anything to warrant you changing your mind -so don't. As I said on my first comment - lie and tell him it's done or just be unavailable when he calls again. If you get letters or emails then get your partner to read them and then destroy/delete them if it the same rubbish. You do not have to engage with him if you don't want to. Write to him if you feel better giving an explanation telling him thanks for the offer of support but it's something that YOU need to do on your own and that you know that he will respect your wishes - he's got nowhere to go with that and if he still pushes it then he only makes himself look unreasonable and you've given yourself permission to ignore him going forwards.