Warnings Restrooms are few and far between. Use them appropriately. Crossing the Peace Bridge is crossing international lines. The customs agents are familiar with birders crossing over for a day of birding and you can mention this fact to the customs agent. If you are a foreign citizen, be sure to bring along proper identification.
Several tolls exist for crossing bridges and such.
Be prepared to have lots of change readily available for faster crossing. Option 2 seems the most inviting since most birders will make a stop there anyways. Option 1 Pay for parking. Option 2 Park upriver and walk downstream. Option 3 Park downriver and walk upstream.