Be sure to check the signage in the elevator at RiverPlace for the social hour timing and the bar specials. Last time I stayed there the social hour was 4-5 instead of the typical 5-6. They were running a 50% off bottles of wine special at the bar one evening; you can take the remainder up to your room instead of trying to finish over dinner.
There is a great deck with rocking chairs overlooking the river that will be perfect for an evening beverage and lite bites in August