If you have the wood cut at builders or wherever, ask them to add the edging for you. Its cheap and doesn't make much difference in the price. If you want you can also opt for 2 or 3mm edging which is more durable and looks even better than the iron on type.
The racks looks awesome man. Are those 11l tubs? I used them for a rack for corns but placed my boa cage ontop of it, the weight was too much for the wheels so I need to go and fix that now!