How to sort photos on ipad

Hi. I am a professional photographer & I travel a lot as my clients are based in different countries. As laptop is quite heavy so I prefer to carry ipad. But the problem is that all my pics get jumbled up & i am unable to show them according a particular theme. So i want something which can help me in organizing my pics. For eg: I want to show my best pics related to nature or wedding etc . then i can easily sort out those particular pics with some keywords etc. Is there any app available which can help me to add tags or keywords etc to my pics?
Thanks

Have a look at Sort Shots

Sort Shots - iPad Edition for iPad on the iTunes App Store

Edit:
Scratch that.... seems OK for lower res images but struggles with higher res stuff