Depends on the ercol colour and the style. You would get more for it on ebay than anywhere else I would imagine, as the popular styles and colours fetch good prices. Only the pale wood sells for any sort of an amount, and only the simpler styles. Hard to say how the value will go as at the moment those styles are fashionable again but that could change. If you like it why not keep one favourite piece and sell the rest?
as hellymelly said, it's only the pale wood Ercol that has much value. You can see on Ebay how much pieces go for (the pebble sets go for a lot). I wouldn't put it in storage, as tastes might have changed by the time your children want it. Why not use it yourself? I have lots in my Victorian house as it's so well-made and comfortable. I thought the blue label was a form of authentication - not sure though.