I agree with your dad that a drobo is overkill. It's a great device, but if you only have 50GB of data, you'd be wasting space. I would suggest a simpler RAID system if you're worried about handling over the years.
My Book Mirror Edition or
My Book Studio Edition II. Your choice should be based on if you use Macs or PCs and what your budget is. I tend to lean toward Western Digital, but other brands are good, too.