"So, the wife and I are going to head out, next weekend, for out anniversary cruise. "
Hmmm, unknown destination cruise with your wife. You're not building up an aliby with us all...are ya?

Does she know how to swim? Just kidding.
The reason I suggested Colonial Beach over Cobb Island is for a couple of reasons.
Cobb, there are a few (3) small restaurants, little grocery store across the bridge. Shymansky's, Captain Johns have dockage but are in very poor condition with rotted deck boards and some slips missing power hook ups, poor restroon facilities, if any.
It's a quaint little island with not much to do. Yes, you can enter from the north end of the island, just hug the reds through the channel but you must shoot for the flashing green marker after the last red channel marker. Don't try to stay in middle, the bend from channel to Neal Sound is shallow off to port.
You can continue the river further south, head up the Wicomico and into Neal sound from the south but is a further trip. I enjoy cruising over there from time to time but try not to make it an overnight stay.
Colonial Beach has more restaurants and marinas all in good shape, easy entrance to safe water. The town is about 1 mile away from my marina, smaller marinas are closer to town. With coffee shop, gift stores, groceries, off track betting and food at the River Boat. Dockside, home to our marina, has great food, a back deck on water with bands on Saturday nights. You can rent a golf cart for the weekend and take in the sights and do as you please. I can arrange a rental for you if you like. I will also be happy to let you use my vehicle.
What ever you decide, let me know and I will assist you however I can.