James, for those shots where you don't have room you could just change the position of the fill. BUT, if you have a little more room why not carry a hot shoe / umbrella bracket and a Softlighter? Very portable, quick to set up, great light. I think your speedlights would have enough power, although I prefer my Bees.

Softlighter: http://www.bhphotovideo.com/c/product/42418-REG/Photek_SL_4000_Umbrella_Softlighter_II.html

Bracket: http://www.bhphotovideo.com/c/product/298709-REG/Impact_3117_Umbrella_Bracket.html

I guess I'm assuming you already carry stands with you for the flashes.