Grand Manan Inn is the classic "old" inn on the island. It is walking distance from the ferry. Haven't been there for 2-3 years, though. There are several birding sites nearby the inn on the NE coast of the island. Check eBird for all the hot spots on the Island.

Bombay Hook has three primary impoundment areas. Each is bounded by an open dirt road to the east. Thus, the sun will be to your back in the morning. Great lighting at sunrise. But difficult lighting by late afternoon. Check the tide schedules to know when the shore birds are most likely to be in the impoundments. At low tide they tend to go to the east of the roads into the mudflats. There is also a smaller area called Finis Pool, off the beaten path but well worth a quick look for birds not as likely to be in the larger impoundments. In April you should also find early migrants in the woods along the roads and at the Allee House. I agree with others, you will need either a good scope or 600+mm lens to get pictures on the back sides of the impoundment areas. But there are plenty of opportunities to be obtained with shorter lenses. At the Visitors Center you can get a birding map of Delaware and find plenty of other great birding areas, if you have time. The NWR opens at sunrise and closes at sunset.