You can try using a bitter spray this helped get our bun to stop eating our baseboards... just fair warning wash your hands after spraying, lol
SynergyLabs Fooey! Ultra Bitter Spray; 8 fl. oz. https://www.amazon.com/dp/B0002DIOD0/ref=cm_sw_r_apanp_2PNdx7XpSIOFW
Please be sure your buns also have protection from the sun, heat stroke is a killer.
As for flooring maybe some wood deck tiles so water can drain through. And they aren't hopping in any puddles?
Deck Tiles - Patio Pavers - Acacia Wood Outdoor Flooring - Interlocking Patio Tiles - 12"x12" (6...
Honestly I recommend investing in a high-end roomba, you can map put just the area around their cage schedule it to vacuum daily.
I pick up the big stuff by hand but its not necessary the docking station will empty the roomba 30 times before you need to empty it so you can easily go a month or...
Here it is: NHILES Portable Pet Dog Pool, Collapsible Bathing Tub, Indoor & Outdoor Foldable Leakproof Cat Dog Pet SPA for Dogs Cats and Kids https://www.amazon.com/dp/B082F1V2VV/ref=cm_sw_r_apan_glt_fabc_F8Z0W7HV3CHE9E7RWW3Z?_encoding=UTF8&psc=1
We have not taken SirThumps on a plane but surely some day we will! Please share your experience if you take Lavender on a plane. I would think they would be just fine, although take off might make them uneasy!
We do road trips with our bun all the time. We have a decent size carrier and will even set up his litter box on the back seat so he has his space. Pretty much open roam on the back seat to himself. But he is also just fine in his carrier for shorter drives.
Honestly if you can invest in a Roomba it will be your best friend... we can set schedules for it and it keeps our bun's play area clean day in and day out!