If you are set on using a debit card, I suggest never using your PIN except at an ATM; run everything through as "credit". The one time DH used PIN at a gas station, we had $800 in charges from another state the next day! I know in our situation that's weird that our info was stolen in one time using a PIN, but it does happen.
Keep in mind you'll have daily withdrawal limits if you want to pull cash as you go; plus the hassle of finding a free/compatible ATM.
If it were me, I would show my DH info that shows the security of using a credit card for travel vs. using a debit card. Credit cards offer excellent protection against fraud, and you have more time to dispute (like up to 90 days for credit card as opposed to 48 hours for debit card!) - and your liability with a cc is limited to $50.
If you were the victim of fraud while using debit, it could totally upend your trip and future budget. You will have to check all charges daily while you're on vacation, and as many pps have noted, you will tie up a lot of your funds with holds. Most hotel/car rental holds have stayed on my credit card for a week after I've cashed out.
You could solemnly swear to each other that the credit card would be used only for the budgeted vacation amount - and you could even close it after your trip if you're worried you'll fall off the wagon.
But it seems short sighted to put worries about overspending on a trip you've likely budgeted carefully for above the protection and hassle-free convenience of a credit card.
You could even use the credit card only for the holds (you can pay with cash or debit when checking out and the hold will just be on the cc until it falls off), but then you'd still have to check for charges on the debit card daily.
What's the worst that could happen with a credit card? Fraud, and they put a hold on your credit card so you have to fall back on your debit (and then you're subject to the "worst case scenario" below. I'd actually get 2 credit cards from 2 banks for the trip.) The most you can lose is $50.
What's the worst that could happen with a debit card? Fraud, and they put a hold on your debit card so you have to fall back on your other debit card, and you may not be able to pay your bills while you are disputing the charges with your bank. Depending on how long it takes you to report the fraud and your bank's practices, you could end up losing some-to-all of the money taken by the thief forever.