We have used gift cards on trips. Overall they are easy to use, but with a few comments if you plan to use a whole bunch:
1. If you lose them, you lose them, just like cash. Unlike cash, they are slippery little buggers. I use them
one at a time.(until used up) I give some to DH, keep some locked in luggage, and wrap some with a rubber band.
2.
Watch your balances. I use a combo of techniques: the first is marking the balance with a micro Sharpie. Cards that are fully used get marked with an X. Otherwise it is very easy to loose track of the balances.
3. Balances are marked on (most) receipts. Take a second to look and check they are correct. I wrap the most recent receipt around the card I am using. It only takes second, and that way I know the balance, and that I'm not mixing up cards. In my experience, restaurants are where mistakes are most often made, especially if you are staying onsite and/or using
DDP or TiW. Some servers automatically want to charge to the room. So if you aren't careful, you THINK the charges went to the card, but they end up on your room bill. Some servers also offer to 'toss the card' for you, but keep it.
If you don't have a system, it is very easy lose track of how much $ you have left on each card, miss some funds, etc.
There is a way to check balances online. After the trip, if I'm ever unsure, I check the balances before tossing.
If you make a return- the balance
GOES BACK ON THE CARD !!!! If you tossed the empty card, you might be out of luck.
So as I use the cards up, I toss them in my suitcase.
If I use them to pay a room balance, I prefer to call the day before we leave, rather than using vacation time to process one card at a time. I mark each card after I read off the code.