Are you going to be local the whole time? I'd recommend that your in-laws start asking around local gas stations or other places with room "out back." Most of the storage areas around here are full and have waiting lists. You can Google "rv storage" and start calling, but a real storage area won't be interested in 8 days.
There are a couple large storage areas in Sedalia, just up the road from Castle Rock, who might take pity on you.
No neighbors with a long driveway? All the members I know in the area are parking their refurb projects on friends/parents lots due to their own space limitations, including me.