Feeding schedule for cats at home alone

I may have to go out of town periodically in the coming months to deal
with my mother's health issues. I used to bring my cats with me (in a
carrier) when I had a car but I've got financial issues that keep me
from being able to afford a car for the time being.

That means I'm likely going to have to take the bus or train to get to
my mother's place and neither of them allow carrying pets in my area.
That means I need to leave the cats at home, which they'd probably
appreciate since they don't get along really well with my mother's cats.
I've arranged for a neighbour friend to come over and feed them and
scoop the litter box while I'm away.

However, I don't want to impose on my friend too much so I'm wondering
if it would be possible to feed the cats only once a day or even once
every second day, assuming we lay out sufficient food? I've never left
them alone for more than a few hours before and I'm not feeling really
good about leaving them but all my cat-loving friends already have cats
and I know that all the cats involved will just get stressed if my cats
stay with them. A kennel is not a reasonable option either; I've heard
too many horror stories about cats picking up diseases from the other
animals at the kennel.

I should mention that my cats are both 15 (years) and in good health.
One is male and one is female and both were neutered at six months. They
get along fine and usually snuggle and groom each other every day. They
normally eat twice a day at 8 am and 8 pm. However, when I had shift
work and couldn't be home for their normal dinner time, I gave them half
their dinner before I left and half when I returned and they coped with
that well so I think they are adaptable.

I'm not expecting to be gone more than two or three days at a time.

How infrequently can I have them fed without causing them undue stress?

Also, does anyone have any suggestions for how I can keep them from
feeling lonely while I'm away? My male cat cried all night once when I'd
left him at my mother's house to work in another city for a week; he was
apparently desperately lonely for me. On other occasions, especially
when I spent a couple of hours with them before leaving, there was no
problem. I'm in an apartment building so I don't want him yowling the
night away and upsetting the neighbours, especially while I'm away.
They've met the friend that is going to be feeding them - once, briefly
- but I'm not sure if they would play with him if he was here without me....


--
Rhino