Kenny, your finances MUST be "much better" to be contemplating renting a houseboat on Cumberland for a week ...LOL!! Seriously though ... Cumberland Lake in the Spring can be a 50/50 call. Flooding rains have messed with the Spring Crappie spawns in most of the lakes in Ky, over the last few years. You may well do much better by returning to Green River Lake. Distance wise, the drive time is fairly negligable. And the state campground area around to the Emerald Isle Marina is as good an area as any to catch some good sized fish. Holmes Bend Marina (on the other end of the lake - river end) has houseboats to rent. Emerald Isle has "condos" to rent.
My excursions to GRL have usually been in late Apr or early May ... and I've usually found the fish to be fairly shallow by then. I haven't been to GRL in a few years - but I doubt the spawning areas have changed much. I've spent most of my Crappie fishing time on Taylorsville Lake or on trips to Watts Bar Lake in E TN (crappie tournament trip). Taylorsville Lake is just a bit less of a drive from Lexington, than Green River Lake ... and that's the main reason I've not fished Green River Lake as much as in the past. If my work schedule will allow, however, I'll be making some Spring trips there, next year.
Before you make your trip down .... contact me on the main board, or here, and I'll see what info and fishing reports I can dig up for you. At the very least I can give you some websites to check on for conditions of the lake and current fishing reports.
Then again, there's always KY Lake & Lake Barkley to consider !! Keep in touch and ............luck2ya ..........cp