So, do we do one stop or two?
Depends on the WX. If you have headwinds and you're beating head seas down the bay, it can be a pretty miserable trip. You'd want a break. OTOH, if you have light N winds, it can be an easy run and you could leave at dawn and go til dark. There are 2 basins in Portsmouth that are free and you could spend the night there- no services, but close to restaurants. Fuel close by.
Dismal Swamp is scenic, slower.
No, you don't tip locktenders! The lock at Great Bridge is restricted opening coordinated with the bridge. It will be a stbd tie southbound and is fendered, you need bow & stern line, they'll take the lines if you can't reach the cleats. It's not a big deal, the lift/drop is barely perceptible. If you have Active Captain, it lists all the bridges, heights, restrictions (schedules), and phone #. If you don't have AC, get some way to access it, best source for current ICW info. You'll call the bridge on VHF 13 as you approach and request an opening.
There are bridges just south of Portsmouth that are listed in guide books that have been removed. The only lift between there and Great Bridge is Gilmerton, it's 35 ft closed. There are RR bridges, normally open, close with VHF security call by bridge number. Do you know your air draft to within 3"? Learn it. The bridges will have a board that tells you the height from the water to low steel. Sometimes 3 or 4 ft additional in the center, there's usually a sign that specifies. If you're close, the bridge tender may give you a hard time if you hedge on an opening request for questionable clearance. They'll quickly relent if you let them know your air draft to that detail.
It's a great trip, the 1st time can be fraught with tension, pay attention to the markers, review your route ahead of time and keep the guide books and Active Captain close at hand. Allow time to stop at a few places so you can really enjoy the trip! Safe travels!