I love Lachlan and think it is lovely with Amelia.

I like Lucy Isabelle Francise. You have 2 longish middle names so a nice short first name goes well. I think Isla Isabelle is a mouthfull too so maybe you could put Francise before Isabelle if you went with that.

I have an Amelia and SIL has a Charlotte. I find when they are together and I call out to them they are a real mouth full to say together, I usually end up just calling out 'Girls'.