As someone mentioned, Cruise America is a big name in rentals. They offer clean, well-kept, newer rentals and they'll help if you have problems on the road. You'll have a lot of choices for RVs. Don't go with a common RV dealer. Go with an actual RV rental. Have a great trip wherever you go. It's a great lifestyle for families.
One driving trip - if you're renting a Class C, where you're sitting will be narrower than the RV part so be very aware of that when pulling into a campground entrance booth area or a fuel station so you don't get too close and scrape the side of the RV. You'll also have to allow a bigger turning area to make turns. If backing up, have your wife go outside and direct you in. Don't try to do it alone. Campgrounds usually have rocks, short posts or trees where you don't expect them.
With your family, you'll need them to know that they can't leave faucets running continuously if you're not connected to a sewer. (dishwashing, hands washing, showers) The tanks will fill up fast. ...and a BIG one - nothing in the toilet except for a 'small' amount of toilet paper and use one full toilet bowl of water to flush big jobs. :) By using enough water you won't risk a dumping problem when you go to empty your tanks.
Also, if you're hooked to a sewer for the 4 days you can leave your grey water dumping valve open so you don't have to worry about your tank filling up, but beginning with Day 3, have your grey water valve closed so that you can be storing some rinse water for your sewer hose for after emptying your black tank on Day 4. NEVER leave your black tank (toilet) valve open to the sewer. You need to build up the liquid in that tank for ease in dumping the solids. For only 4 days of use you shouldn't have to dump your black tank until you're ready to leave. Even then, if your tank monior shows your black tank only 1/2 full at that time, hold down the toilet flush peddle and fill that black water tank just before you're ready to dump it so that you'll have at least a 3/4-full tank of liquid to dump. This provides a good emptying of the tank. You need all that liquid for things to move freely when you do dump. Also, after first dumping the black water, close that valve and then dump your grey water tank. This will be enough water to clean out your sewer hose from the black water. Please don't hold your sewer hose under the fresh water faucet where people connect their water hose for their fresh water use. That is a very unsanitary practice and it's not needed that you run good tap water through your sewer hose to rinse. Your grey water tank contents will be clean enough for your sewer hose. Think about it! :) You're not going to disinfect that hose no matter what you do!
For your first time you might want to look for a campground with a sewer connection but still conserve water so they get used to doing so if you don't have a sewer on a later camp trip. It would also be fun if you have a friend or relative who has a camping unit to go with you. You'll surely have lots of questions as you're doing things - even opening the awning. If you don't go with someone, definitely feel free to ask your camping neighbors for any help even if you think it's silly. We've all been in your position at one time! RVers are very friendly and eager to help. Have fun!
