Anything done to get a camera out and get more use increases it's value to an owner that bought it to make photographs. As far as going up or down in terms of selling, prices are generally down anyway. So using them is the best thing going.
You could get a cute little CL for child #3 to use in their toddler years. Nikki did prefer the M3 when she was 4. Really hurt, name a child Nikki and she prefers Leica.