sdsurfer, how big is your lot (in Encinitas)? Since you are in the family-growing-and-raising stage, I don’t see you being able to stay in your (coveted) Encinitas if you later decide to sell and then shop for a larger house in the future. I see you having to shop in a lesser-desirable community such as PQ, Poway or Esco or the various new developments in SD County’s “lizardland” where you will pay MR into oblivion if you wish to remain in SD North County.
If your lot is adequate for it, it is cheaper to add-on to your present house than move, IMO. I don’t know what part of Encinitas you live in but if your lot is over 7500 sf and you do not have intermittent train noise, then I feel you will be able to recoup the cost of a major remodel or addition in your sales price when or if you decide to retire elsewhere.