Oh, my, you'll need to bring lots more stuff! The rule is: "If you bring it, you won't need it. If you don't bring it, you will NEED it"
Things that come to mind:
Feed/hay
feed/water cups/bottles
Absorbant bedding for carrier pans (pine shavings, litter, etc)
Baby wipes (quick clean up)
Alcohol
Peroxide (in case someone pees on themself)
Cotton balls
Q-tips
Nail clippers
Wire cutters (in case someone chips a tooth, cut them down evenly)
spray bottle for water
brush
bag balm
septic pencil (for any cuts to stop bleeding)
Pen/paper
DUCT TAPE
Permanent marker
Pedigrees/records
Reading material/ipod/laptop/portable dvd player (things to pass time)
That's all I can think of for now. Most can fit into a tackle box and be ready to go.