congrats -married 5 years here, we've had our ups and downs but its been worth every minute.
i drive my rv
it gets a whopping 10 mi to the gallon (im taking it out to wyoming in a week for the rainbow gathering) i will be doing some aero mods to it which will help and it will be loaded with 10 people and lots of gear, plus i wont have to stop for many restroom breaks (mainly my own which is usually when i fill up also)
once i get to my destinations though i walk or ride bike, sometimes i drive if i towed another vehicle (i usually get slightly better mpg when towing so thats a bonus) but my next trip will be all walking. as for my driving style, rv's can only be hypermiled so much do to the aerodynamics, i casnt P&G mine but i do coast to stops, in an rv people are more understanding about that (i usually tell passengers that it helps with stopping if they even notice) also i will not drive over 60 mph
again congrats on your wedding