What type of wire should I use to connect my buttons/sensors from 3 feet away?
Adding a length of wire to each device will increase their resistance, but generally no more than 20 ohms or so depending on the gauge of the wire.

For a button using the internal pullup the overall resistance must be less than \${{20\text{k}\Omega⋅0.3}\over{0.7}} \approx 8.5\text{k}\Omega\$ or so in order to reliably register a low. Adding 6 feet of wire (3 feet towards, 3 feet back) is unlikely to cause the resistance to increase that much.

The pressure sensor is a variable resistance device however, and as such may require recalibration when connected to the wires if the actual value is used rather than just using it for presence sensing.

Also note that longer wires pick up RF more easily, so you should consider twisting the pairs connected to the device (or using twisted-pair wire in the first place) and using ferrite beads/toroids and/or common-mode chokes to suppress the disturbance caused by the RF, especially in an electrically noisy environment..