Honestly go local, there is so much close by to you that you don't realise.
A one and three year old won't care how far you drive really.
Call the local fire department ask when they give tours things like that.
Do some things in your house declutter, paint a room, get some pictures hung of the kids art work (grab them some canvases and paints).
What about visiting people you know? (no motel
Renting/borrowing an RV for a long weekend?
OHHH the cheapest summer way to stay someplace go to the university residences I think last summer my dd and her father stayed at a big university for 30 dollars a night with a kitchenette.
Sometimes places have sleep overs, our zoo and science centre have sleep in the centre (cots).
And spread it out why not take one long weekend a month?
Pumpkin trip in October, etc.
also call the local tourist boards coupons for things rock.
check your airmiles for tickets, motels that's cheap if you have them.