I strongly recommend Full Auto. I have a personal trainer who owns a gym (www.eptsomaha.com
) and for several years they just manually run the credit cards themselves. It would take several hours to complete (as each trainer ran different cards etc) - and like yourself, sometimes they'd be too busy and not run it for a day or two, or a week or two. This creates frustration not only for the trainer, but also the client as they expect to be billed on "X" day.
For my wife's SEO company, while she could run manual each month, she too went the automated route. It's just one less thing to think about.
Going one step further. My employees are paid for 40 hours each week automatically. While they still submit timesheets etc and I can adjust the hours up or down, by default they're set to pay out at 40 hours so that if for some reason something happens and I don't get in to edit things, they are sure to still be paid.
As for who would be in charge, you really need two people involved, and preferably not the other person that's going on vacation with you
Both being out of country at the same time never helps!
Automation is the recommended path whenever possible. Any time you can automate any specific task that is redundant, then you're freeing yourself up to do other things --- not free time, that never happens!