Umbreon and Espeon IV/Nature for Colosseum

[Cezanym]

I‘m on a Journey of playing all pkm games and during that Journey I want to keep the rare and important ones such as these starters. I also want them to have my desired IVs and nature. Usally that‘s no bigi, but this case is rather odd.

For Coloseum Pid, Tid, Sid, IV and nature are intertwined as far as I know. 

I want to create or edit my starters, to have 5 Perfect IV‘s and 0 on Atk. Umbreon should be calm and Espeon should be timid. 
I want them to share the same Tid meaning I want them to come from the same seed. 

If anyone can educate me on how to do this I would be really glad(TW: I‘m really stupid when it comes to coding and I‘m on mac). The Pokémon files would also be fine.

Tyyy in advance