This is just my opinion. Personally, I'd stay away from putting a wood floor in the basement. Just because it hasn't been wet in 7 years doesn't mean it'll never get wet. I live in an area that's prone to basement floodings, you may not.
The vapor barrier won't hurt a thing but it's not gonna stop a flood.
About the sheathing. I prefer a 3/4" fiber board (not particle board)on 16" o.c. sleepers. 24" o.c. makes for a bouncy floor.
One other thing, if you go ahead and install and get flooded someday, you'll have to put up with the smell until your insurance company, finally, decides to give up the money, which could take months.

Kevin

One other thing. I'd use glue and some kind of anchors. Tapcons work very well. The anchors will hold things down tight and the glue will help to prevent squeaks.

Kevin

Use 3/4 inch tongue and groove plywood. Overlap the seams, ie) stagger the sheets.

Do use a mechanical fastener with the glue. Don't rely on glue alone. Use 16 o.c.

Put rigid insulation between the sleepers to minimize the echo of footsteps.

Vapor barrier isn't necessary but you can test to see if you need it. Tape a 3' x 3' plastic down - seal all around. Come back in a few days to see if there is any moisture between the floor and the plastic.