If you make sure that you have GFCI protection on the hot wire ( either in the wall outlet itself or with an adapter plug), that will GREATLY improve the safety of the system.
You should be able to combine all of the neutrals safely, as that is a standard for home wiring, but with 5 wires, you are going to run out of room in a simple wire nut...I imagine that is why the guy @ Lowe's brought up a bus bar. You can use wire nuts by themselves, but you will be running a lot of pigtail jumper wires & honestly that's a pita.
Instead of using the term bus bar, look into either power distribution blocks / terminal blocks. Those are the same things as using a bus bar, but are more easily contained in a waterproof housing and hidden.