We too have a 2300, 2013 Chevy chassis, 30mo old, just over 30k miles. Also getting 10.5 to 11.5 mpg, 10 mpg when towing 2007 Malibu. Wife and I are in our 70s, and frequently (when we can) travel with 2 granddaughters. Similar experience to yours. Just a few thoughts to share:
1. After market passenger side seat swivel is an excellent add on. Got mine from Shop4Seats.com, about $240 with shipping. Easy do-it-yourself install.
2. I had age related problems crawling out of the corner bed until I added 3 door handles to the underside of the window overhead cabinets, plus one on the wall opposite side of the frig. Purchased from Amazon, JR Products Assist Handle. Wide handles will not work. These are narrow enough to screw into the cabinet framing. They aren't strong enough for lifting your body, but work good to steady you when rising from bed.
3. Another help with the corner bed difficulties, invest in a Grip'n Grab Stick. Got mine through Amazon. Medium or longer length works to open cabinet doors, move pillows, and make up bed while standing on the floor.
Have several other "improvements", but these are the ones that make the most difference.
Have fun! We do!