I think it's beautiful. It flows really well and sounds classic and timeless. She'll probably have to correct people on the spelling from time to time, but "Rachael" is perfectly acceptable (read: not made up), and I like the tie-in with your H's name. If you'd said something like Raychyll, it would be a different story, regardless of your reasoning, though.
Re: your thoughts on our choice
it's not though, it's Richardson, DH loves how Rachael Richardson sounds
for a boy we thought Collin Matthew Richardson
A very pretty name - very classic.