You may be too late for the seabird cliffs - the birds tend to disperse by late July. South Stack is still a good place to visit for Chough, and you never know, there may still be auks about. Also should be Manx Shearwater passing out to see.
You might also want to drop in on the Ospreys at Glaslyn near Porthmadoc, They should still be around - we visited at the end of July last year.
Otherwise, Conwy reserve is always nice if you fancy a trip along the coast. Foryd Bay near Caernarvon can be good for waders. Black Guillies may still be around in Holyhead Harbour. Cemlyn on Anglesey is good for terns and is a really nice spot but again not quite sure when they may be off.
And with August, who knows, could be the odd migrant. Have a good time.