The first,
Elliott because I think that's considered the "common" spelling and would be how most folks would spell. The others just don't look right to me, like they're missing something (a letter! haha :P)
My PNL = http://www.behindthename.com/pnl/37275
Top: Henry & Lara (main) and Caspian & Briar (GP)
Bottom: Trajan & Jacoba (main) and Dinadan & Melpomene (GP)