I set my goals a little higher, I did four a day for ten days straight.  

My secret? lots of beer and tequila. lol

I will confess, much of the time I was shooting mainly air with hardly any volume of ejaculate worth measuring, a thimbleful at max by my third or fourth time of the day.

At age fifty, unless you have any medical conditions you didn't measure, having a full 24 hours to recover in between sessions shouldn't prove too difficult. There are a lot of guys well into their sixties still getting laid every day.

If you really are worried, I would ignore my advice about tequila and beer, staying "well hydrated" is helpful if you are going to have a lot of sex, although I really don't consider once a day a "lot"

Volume? Of the tadpoles?

Do you intend to get some of these women pregnant?

If not, why do you care about volume?  I guarantee you that's not important to the providers.  

Now stamina--that IS important!  Since your trip is this week, it's too late to do much about your stamina.  In addition to getting enough rest and eating healthy, avoid drinking too much alcohol.  All of which may be hard to do while you're traveling.  Good luck!

It's too late for it this time but I highly recommend testosterone supplements after you get the AARP card.  
Not only good for mr happy but helps all over.  
I've found 5 hour energy helps out in the timeframe you are talking about.

and so far, they've been serving me well:

Goji berries steeped in green tea with ginseng.

Walnuts.

Peach brandy.

Also, hold a cold glass of water with your testicles in it for about 2 minutes once a day.

I've been doing this for about ten years now, and still going strong at 63