@Globocnik 

With respect to the house if you need more coverage, then you can add another M9 node (up to 10) to maintain your mesh network. With the pool house, you can get the EAP225-Outdoor which is just an AP unit, and run a cable from one of the Deco nodes to that which should give you coverage outside. The EAP will provide omnidirectional coverage. The EAP will not work in a seamless mesh with your existing Deco so I would recommend naming it different so anyone outside knows what network to connect to in order to have the best signal.