The esp8266 isnt all that compilocated, allthough I've been faffing about to get it working.
I think its sensible not having moisture sensors, you'd need a load to make readings meaningfull, the caravan pump sounds a good idea, I have 2 55gal water butts a few meters away, I alsohave a load of brake pipe left over from fixing my old shed, so that might be handy too.
DHT11's are good for temp & humidity, the good thing with the esp wifi device is that the thing speak website allows you to upload data and they will graph it out for you over time, for minimal effort and no cost.