What airlines? The Sheraton only makes sense if you're using T2 and even then, IMO it would be nicer to do a day rate at a downtown hotel so that you can come back to the room to rest if desired in the middle of the day. I'd pick something very close (walkable with whatever luggage you'll have then) to a RER station on the line from the airport or CDG airport bus stop that's also close to some stuff you want to do.

I'm not sure what downtown hotels offer day rates. You might need to contact the hotel directly if you can't find something on a chain hotel's website. Pay attention or negotiate the specific hours that you'll want the room; standard day use rates often are 9 am to 4 pm.