what are the easiest notes for trumpets and clarinets and french horns please?

[lingle]

we've got trumpets and clarinets (both in Bb) and a french horn(in F) in our school orchestra.

this term they've played mamma mia in concert pitch F (that's G for the trumpets/clarinets and C for the horn) which worked well.

I'm thinking of Dancing Queen and Spring from the four seasons. Is it easiest for those instruments to do the pieces in concert pitch F or concert pitch Bb?

I arrange everything myself so don't need to buy in sheet music.

I know that for flutes and recorders the easy notes are GABand C - would love to know the equivalent for trumpets, clarinets and horns.

thank you!