Residence in Spain

Depending where you're from, and how often you'll be leaving and coming back during your 2-year "vacation" ... you may not have any other option than being a "resident".  As per driving (I'm from the US) I know that there is a 6-month limit to driving legally here as a tourist, once that limit is passed you can get a pretty hefty fine, plus lose the "right" to legalize your driving situation for 2+ years ... Along the lines of taxation, well, that's another story. Work, rental contracts, etc. can all be influenced by a resident or non-resident status. 

You didn't really go into details on how/why you and your family will be here for 2 years, so it really is kinda tough to give you advice.  Maybe just ask the person at the bank...or your employer (if you have one). When I began my 13+ year stay here in Barcelona in 1999 I don't think the bank even asked if I was a resident or not ... I did NOT, of course, have a N.I.E. (Numero de Identidad de Extranjero = Foreigners Identification Number) at that time so that must have been the deciding factor.

Let me know if I can give any further advice ... good luck!