Hey, that's a perfect slogan xD We could promote the 7th September now
Aww, Nezumi being young and in West Block is a perfect idea!
I'd leave the 6th as just Shion's birthday - maybe a double topic as in 'The Day they first met' but nevertheless, Shion's birthday is more important
at least that's how I feel .... I think there'll be a lot of things about them being young too but this way you could also ... do special things for Shion's birthday specifically ^^ This way it isn't narrowed this much.
Maybe the 7th could be Mini-Shion & Mini-Nezumi Day? Because I already adore this idea. It's quite fitting I think. Because of the new life they both are going to live from now on ...