I have beached houseboats side-by-side many times. If you are renting, it is very likely that the generator exhaust is a tall vertical stack that will not be affected by another houseboat. Two houseboats will require only 14-16 more feet of beach space depending on the boats of course. It shouldn't be that difficult to find good beaching locations. Once you have found your location, here is what I have found workable for beaching two boats. When you get close to shore, but before beaching, bring both boats to a complete stop. Then bring the two boats side-by-side very slowly. Use all the dock fenders available between the boats and lash the boats together using strong rope, while floating, using as many cleats as possible. Use caution to keep feet and hands from between the boats. If you have children on board, I would keep them inside the cabins until the boats are securely tied together and beached. Once the two boats are securely lashed together, use all four engines to beach the boats. It is likely that the lake will still be rising at that time, so I would beach them as solidly as possible. And if you are doing a "hard beaching" be sure all passengers are seated and hanging on for the sudden stop. Two anchors on each side, if properly set, should be plenty. Also, with the rising lake, I would set anchors at the bow. The last time I was on the lake with two side-by-side houseboats was in mid to late June 2014. I had to re-beach the boats every day due to the rising lake level. Not a big deal and only takes about 10 minutes with a little coordination and a crew willing to follow instructions. Certainly there are other ways but this is what I found workable: (this assumes the engines are in plenty of water and the stern can swing back and forth about 5-10 feet) 1) have six competent crew, 2) disconnect the bow anchors and be sure the anchor lines are not in the water, 3) place a driver at each helm and four crew at the stern, one for each anchor line, 4) un-cleat all four anchor lines and pull up any slack, 5) start the engines and use all four engines to push straight forward as far as possible (full throttle, then back off) - the four line-tenders at the stern need to keep the anchor lines tight at all times, 6) keeping all four engines in forward (moderate the throttles) turn both wheels to starboard (right) to swing the stern to port (left) a few feet - have the line tenders on the port side pull up the slack and when the swing to port stops, cleat off both lines, 7) turn the wheels to port to swing the stern to starboard - have the starboard line tenders pull up the slack as the stern swings to starboard and when the swing stops, cleat off both lines. 8) this process can be repeated, back and forth, as needed to wiggle the boats up onto the beach and then eventually cleat both sides off when far enough up the beach and the boats are straight. 9) re-set your bow anchors.
Good luck!