I'd just go for the front, unless there is something of interest on the back. Alot of the times when I look through peoples cards i just skip straight over the back if they have it.
I wouldn't waste your time scanning all that it would take forever.
Unless special numbering or other players are on the back. Or something you really want to show.
However, showing front and back is always cool. But takes much time.
I say do both sides, like Col said if you do front and back for specific cards only, the others will feel left out. Plus it's cool to see the backs as well, the certification is sometimes interesting. Plus some older unnumbered Topps gu cards have that cute little hologram on them Front n back!