I always use my debit/credit card like it is a credit card. Mine is with a credit union from another state and I had trouble when I first got it with it being recognized as a debit card.
I too thought that as a credit card it did not have a limit, but mine did. Found this out when we went to "look" at new Infiniti G35 for DH and wound up buying one on the spot. We made a transfer for the deposit and I gave them my debit/credit card to use and it was declined for $4k. But finally after several attempt at lowering the amount it went thru for $1500. Found out we had a max daily at that point.
I guess in all my trips to Disney I never went over that amount for a one time charge because I did not know about there being a limit as to what you could use. Seems kinda odd because it's MY MONEY!!! But, I would call your bank and find out. You could always have a payment done halfway thru your trip if you think you will go over your max.