Several years ago we were heading to Disney right after work. I rushed home, changed, loaded the rest of the car. First stop I discovered I did not put my money clip in my pocket. No money, no driver's license, no problem. We had more than enough cash with what my wife is carrying.
If you want to tip mousekeeping, determine the amount and put it in envelopes with mousekeeping written on it. I have left money out before and it was there when we came back. I agree with some of the above, that having some cash on you is wise. Systems go down. (If Uverse was running the systems, I would triple the amount.) I carry a $20 until I break it and it gets below $15 and add a little more. Often, it may take days to break the $20.