This question depends on so many factors!
See my DH is an Eagle Scout and a scout master. For him a vacation means back packing 150 miles into the mountains, carrying everything he owns on his back!

My boys are the same way. To them a day in the park (unless its summer) doesn't wear them out.
Here are some factors that will make it more labor intensive for you:
1. weather .. the heat of summer will wear you out quick, making more resort time a must to keep that fun vacation feel ESPECIALLY if your a yankee and not use to 100 degree weather!!!
2. How in shape you are! DH and I are in really good shape. We have been with friends/family that have been out of shape and a little "fluffy". By the end of the day they were DYING trying to keep up with us and we felt like we were being held back hahaha
3. How many younger kids in your party makes a big difference. Even the best of kids need to be watched out for and taken care of. A couple with no children can get a lot more done during the day while still having a relaxed vacation feel.
4. As stated the time change can make you feel out of sorts! For our family its only an hour time change but for some families it could be a 3 hour time difference!
5. Where you are staying can make a big difference too. If your staying at a monorail resort, the travel time and fighting with transportation is not an issue for 2 parks. It doesn't SEEM like a big deal but by the middle of the week and your standing at the bus stop watching 3 full busses drive by on the way to YOUR resort and your tired and want to just relax.. IT CAN MAKE A HUGE DIFFERENCE.
6. Where you eat can also make a big difference! If you pick all character meals or loud "zoo" type places your going to wear yourself out quicker making it not seem like a vacation. We always try and reserve TS in the middle of the day for a quiet (or at least quieter) location. This is REALLY important for our family. It gives us a midday "break" from lines, and the general hub that is Disney without leaving the parks. Some people prefer to go back to their resort miday and we prefer to have a long quiet lunch in the park.
Room serivce breakfast is a must at least twice while we are there so says MOM
Also BEFORE you go make sure everyone has their jobs to be responsible for! You don't want mom coming back to the room, bathing all the kids, getting all the clothes out for the next day, going over the plan for the next day, changing ADR's, washing any clothes, putting the kids to bed, and general organizing of the suitcases to fit all the junk you bought that day!!! Remember MOM is on vacation too! Your party is only as strong as your weakest link so if there is only 1 person doing all the "work" that person will be your weakest link
