I only lived in Tidewater for three years, but I've been back many times since then. In August there's frequently more traffic on the Hampton Roads Bridge-Tunnel on weekends than during the week, as people on the Peninsula (Hampton, Newport News, and even Richmond) head to and from the beach. The worst times are Friday evening and Saturday morning eastbound, and Sunday afternoon/evening westbound. In the past few years, with the opening of the Monitor-Merrimac Bridge-Tunnel (between Suffolk and Newport News) things have loosened up a little, but if there's an accident (or a car with a blown radiator, or a traffic lane closed off for construction - as at least one stretch of the freeway usually is) on I-64 the trip between the Peninsula and Virginia Beach can take as long as two hours. On more than one occasion I've spent an hour on that infernal bridge between Hampton and Norfolk, sitting practically still, afraid to run the air conditioner for fear the engine will overheat and make things even worse.
My suggestion would be to look for a motel Southside (Virginia Beach, Norfolk, Portsmouth, Chesapeake, or Suffolk). There are quite a few clean, reasonably-priced ones (Red Roof Inn, Econo-Lodge, Motel 6, etc.) right off I-64 and the various other Interstates. My wife and I frequently stay at the Red Roof Inn in Chesapeake; it costs something like $65 per night. It's about two minutes from I-64, and less than half an hour from the convention venue. If you can't find a room Southside, try Hampton or Newport News - and keep your fingers crossed, and try to avoid the peak traffic times.
My favorite of all places to stay in Tidewater used to be the Chamberlin Hotel, a grand, old-fashioned place on the grounds of Ft. Monroe in Hampton. In its glory days (my family stayed there for the first time in about 1966) it was a fabulous place, with a swimming beach, ballrooms, two or three restaurants, recreation halls, its own movie theater, etc., etc. On a Wednesday evening in the summer time you could have dinner in one of the restaurants and then sit on the veranda listening to a concert by the Ft. Monroe post band in the park next door. And if you had a room on the "water side," you could spend hours watching the ships pass by. (I remember watching a helicopter land on board an Essex-class carrier the first tiem we stayed there.) The Nautical Research Guild, in conjunction with the Mariners' Museum, held some of its annual conventions at the Chamberlin. Rick Atkinson's book about Operation Torch, An Army At Dawn, describes how, the night before the invasion fleet left Hampton Roads, there was a steady boat traffic between the warships and the Chamberlin.
Unfortunately the old place started going downhill in the eighties or thereabouts. The last time my wife and I stayed there, in 2001, it was looking a bit seedy - and was practically deserted. A couple of years ago it closed down completely. (So did my favorite Tidewater seafood restaurant, Keith's Dockside, a few blocks away.) Every time I drive up there now I halfway expect the familiar silhouette of the Chamberlin, which has been visible from all over the harbor since the early twentieth century, to be gone. Maybe some historic preservationists will be able to save it (demolishing an historic structure on federal property is quite a bureaucratic process), but I'm not optimistic. If the Chamberlin does fall to the wrecking ball, I sure will miss it.
Sorry for the dumb nostalgic ramble. Bottom line: if you don't mind driving a bit, I don't think you'll have trouble finding reasonably-priced accommodations in Tidwater.
Update six years later: the Chamberlin has now been re-opened as a posh retirement home. I'm delighted that the grand old building has been saved, but it obviously isn't available for convention lodgers.