A big welcome back to the forum.
Honey is so gorgeous and has such a beautiful face.
Happy soon Birthday Honey!
Yes, watering food can help, especially if they need to drink more and/or have few teeth left.
With not walking enough, which can limit their poops, I sat a lazy senior (she had no mobility issues, had been lazy since young, her humans said) and I would carry her away from the house, so she’d be more likely to start walking and have to walk back.
She was hilariously lazy — would flatten herself, and sometimes back herself into a corner, to make it harder to pick her up for walks. Her humans said to drag her if needed, but I didn’t have the heart for that.
She’d poop and pee right by the house and run to the door to be let back in, trying to avoid walks. She’d bark, bark, bark, like open the dratted door immediately. 
I’ve never met a lazier dog.
One of the other seniors I sat had few teeth left and was blinded by cataracts. I noticed it took him a long time to chew baby carrots, though he loved them. His sidekick would steal from his share. I started cutting them in half and doling them out slowly to him, so his buddy couldn’t snarf them down.
Keeping an older pet comfortable is mostly about regular vet checks, softer exercise, and paying attention to small changes in appetite or mobility. 
@Jenny, in each case we certainly took a deep breath and evolved our mindset.
- Agreed clear contingency plan with pet parent. Before pet parent departure we re-read Welcome Guide; re-verified accuracy of exercise, health, vet details/billing; and discussed what-if with pet parent (e.g. contact local family member, owner, vet, … and vet instructions)
- Applied elevated monitoring during housesit. Senior pets - arguably like senior humans - often need a little extra TLC and flexibility. Each day we assessed pet condition; impact of pet exercise; eating/drinking; medication. In each case, we applied a cautious mindset and adaptable plan. For example, dog walk route may be closer to home so able to return home if dog becomes tired. Or taking dog in car to walk/time location rather than walk there. For example, with such a cat we monitored food/water intake and engagement.
In one case the owner presented us with a completed, signed ‘Temporary Guardianship’ form that expressly authorized us to make medical decisions for the pet.
In most cases, only once has a very-senior pet had behaviour/care needs that were undisclosed in advance. For example, bladder/toilet issues. In that case we had no choice but to adapt pet care (frequent toilet breaks outside) and reflect this in the review.
Mercifully we have not [yet] had a pet pass on our housesit. Getting old sucks, for pets too.
There have been a few listings where the responsibilities section was written long before the pet aged, for example it said that the pet enjoys long walks when in fact they now can only manage a slow stroll around the block. Or no medication when they now need some daily pills .
It’s always good to discuss the pets current routine with the host before confirming a sit in case there have been changes since the listing was created .
Thank you 
Thanks so much for sharing @GotYourBack 