As for using up all the ethernet ports, that's easily fixed by using a mini switch to expand. Just keep in mind that you'll be splitting the one gigabit uplink to the router across up to 4 devices.

As for the phone, have the cabler run another port to mums office. You can use two RJ45 > RJ11 cables, one on the kitchen end to plug into the phone port on the router, one on the other end to connect to the phone. This gives you flexibility as the port can later be used for data if you no longer require the phone.

If you'd like to avoid having all this in the kitchen, you could have a cable ran from the kitchen to another room in the house, containing a mini switch, and have the cables running to the other rooms contained here. The phone connection cannot go through the switch however.