Rest your weary head

Nap time over the last 7 months has been totally messed up.  First off when moving it isn't always possible to get naps when they are needed, and second the kids are growing and changing so much that their needs are also changing in the area of rest time.
Now that we are settled into our 5th wheel I'm trying to discover their nap time needs.  I know that where Caeden did not require a nap before when he was inside all the time, he now plays so hard every day that a nap is absolutely necessary.
Any day that we happen to be driving at 3pm will result in all three of my children snoozing in their car seats. So you would think that nap time would move easily to 3pm from the previous 1pm time it used to be.  I would however point out that 1. A carseat keeps my overly active 5 year old still in a way no other thing can, and 2. My children share a very small room in the 5th wheel.  Micah is easy to fix.  Put him to bed in my bedroom with pillows to keep him from rolling off the bed.
Sapphira needs her nap but has never done well at going to sleep.  Caeden needs the nap and if I could get him to slow down he might take it but he is insanely active.
Putting them in the room together results in a lot of play,  putting them in separately results in me getting nothing done and them laying down but not sleeping.  Putting them down together with me seated in the room changes nothing.  Just quiet rest time where I do nothing, get no relaxation, and they do not sleep. 
What is the solution?  Any one got any ideas?  Playing hard is resulting in a grumpy girl, a boy with more frequent accidents at night, and a mommy who is going to go bald.  If I try to slow them down there are other undesirable affects...so really I'm just looking for a nap time solution.
Any comments will be taken into serious consideration.  Thank you in advance.