HELP!

I have heap (and I mean a heap) of family slides from my SIL that I am going to scan and put on a disc for her. My scanner is a Epson V500.

My question is....what dpi should I scan them at?? 800, 1200, less???? These are not for blowing up to a 10 x 8, but I still want a good decent amount of detail....minus the HUGE MB that I will get if I go really high.

Any other useful information when scanning these would be sooo appreciated....new scanner and new to scanning!

Thanks in advance.