As long as you have a place to take them to when you get there, I don't think that it would be unfair. If you have had them for 8 years and left them behind for any reason other that you just could not take them safely, now that would seem unfair.
Good luck on your move!
8 years - they will love anywhere they go as long as you are there, I think. Part Irish, but never been to Ireland My daughter and I have been to Spain 2x and we loved it! Madrid, Toledo, Granada (El Generalife - the Gardens at the Alhambra - are soooo... beautiful), Nerja, Tarifa, Sevilla and Segovia. It is a wonderful country!
I think it will be fine as long as there is a place to stay whil everything is been sorted out in your new home. As long as the cats are happy and depending on there poo habits they should be fed before u leave.
Las expresiones mas importante en Espana:
Mis gatos bonitos
Mis gatos especiales
Mis gatos malos
(my pretty cats, my special cats, my bad cats Nummies!)
I think the last is the most important.