A possible option for you is via the S1 form.
If you have paid UK NI over the last 2 (or 5) years you may be entiltled to health care in Spain under the S1 form for a limited period of time 12 or 24 months I am not sure as things do keep changing
I would ring Newcastle and ask the question
For further advice, contact the Overseas Healthcare Team (DWP):
Overseas Healthcare Team
Room MO601, Durham House
Washington
Tyne & Wear
NE38 7SF
Phone 0191 218 19990191 218 1999 (Monday to Friday 8am–5pm).
Nothing ventured nothing gained = worst they can say is no
Another solution is if you are your husband register as autonomo (self employed) and pay the monthly "NI" (minimum payment is approx 230€ per month it is not income based but a fixed payment), you will get cover. Obviously you will have to register as working (window cleaner, builder, mecahnic etc etc etc) and declare income from zero to xxxx. You will aslo have to get regsitered and will require assistance from a solicitor - I think the ste up fee starts at 80€.
In Valencia region there was a system where you can join the health scheme by paying a monthly fee but not sure if that still exits
Getting a job with a full contract is difficult but last option
In all cases you will have to register on the padron and obtain a certificate of residence (aka residencia). You will probably need all of these for the schooling of your children
Last option head back to UK and rent somewhere
Good luck