I assume Ashleigh (and NyahFaye) would have to take their own path to residency. Not sure how Alex would be treated if he became resident but then turned 18 some months down the road.

Residency-wise as EU citizens you either need to work here or have sufficient savings in order to register as resident, and if you go down the latter route then you will need to show private health cover.

If the wife is a UK citizen then that might need to be done once everyone else has registered. Then - unless there is a local job offer with visa and all - the spouse will need to apply for residency via the "Family member of an EU citizen" route, and the onus will be on the husband to prove that he can support his wife financially (local job or bank balance + health insurance). It takes a few months (mostly waiting and possibly coming back 1-2 times with additional documentation), is a bit cumbersome, but it can be done and you just need to stay positive because in the end you will get the green light and the application will be approved (and residency card issued).

The good thing is that from the moment your wife applies for residency she can remain in Spain legally for as long as the application process lasts (in fact her residency card, once issued, will have the application date as the issue date so it will be valid for 5 years from that date, not the date of approval or card issuance). Don't plan any long vacations during that time though as any letters you receive requesting additional documents to be provided usually give you 7 days to do so in order for the application process to remain open.

In terms of jobs there might be a requirement that it is local, as for the bank balance it most certainly needs to be local.