Alayna does look a bit invented to me - I’m guessing it’s a variant of Alana but it could easily be a variant of Elena too. I think she’ll have a lifetime of it being misspelt.
Ellis is very much a boys name where I am in Wales, so I’m not keen on it for a girl.
Kate is nice classic, and works fine with a short surname- might make it more “punchy” and therefore memorable actually. Some people might assume it’s Katherine on the BC, but it’s not a big deal to occasionally have to say “No, it’s just Kate”.
Rhiannon and Alicia are also nice - and Rhiannon is well known enough outside Wales (thanks to Fleetwood Mac) that I don’t think the lack of a Welsh connection matters.
Eilidh only works well if you are living in Scotland? (the couple of English ones I’ve met spell it Eily for ease). If you are Scots, what do you think about Vaila? I’ve always thought that pretty and underused. Or Morven?
I’m guessing you are in Scotland since you used the Ruari spelling - it’s not a personal fave and neither is Cameron but nothing wrong with them as such.
I do really like Brodie and Lewis (and also similar style Fraser, Callan and Laith?).
Like Kate, Ben is a nice simple classic that sounds punchy with a short surname (but again he’ll have to get used to the occasional “Benjamin?” but no huge deal).
If you want a fairly timeless classic, I’d go with Kate and Ben (I know a couple of Kate and Ben/Katherine and Benjamin sibsets actually, of different ages). If you want something that stands out a bit more (area dependant obviously), then I like Rhiannon and Brodie - don’t think it really matters that one is Welsh and the other Scots.