I don't want to rain on your parade, but at the present time, unless you are very wealthy( in which case ignore the rest of this post), it is not a good idea to bring children out here. It would be the lack of support that would worry me. would you work in Spain?If so, what would you do if one of your children was ill or in hospital, needing you with him, as expected, 24 hours a day. I have been in that situation -it was awful. Don't be seduced by the sun, so called cheaper lkiving costs,family orientated way of life, bilingual children etc. You need the whole family out there. you may cope well in UK when your husband works away for 3 weeks-it's so different in Spain. If he was working in Spain, paying into social security the family would be covered for health care. As he isn't, can you afford private health care( doesn't cover existing conditions)
No NHS dental care-if your children needed orthodontic care, braces etc, it's private and very expensive.
Contact the tax office in the UK, and find out about your tax status-if you are not making a tax declaration in Spain, it will affect your life medical care etc.there in many ways. Even if your husband is financing you from the UK, if you are not registered on the Spanish tax system, you may have problems as you have to prove your income for residency..many, who have lived under the radar for years in Spain, not declaring anything, are now having to toe the line.
Contact the DWP for advice.
I have seen families move out here, and many return to UK-no work, lack of money the chief reasons.It's such a huge undertaking to come out here, and a nightmare to return home if it doesn't work out. I just think it's not fair on the children.