Arien charges in pretty well all combat, so I think Raven was making an assumption.
The circles are trees, not boulders. Sorry, I know it is a crude and rude map.
A word of caution to your plan. Now I am the DM, reportedly evil although I deny the allegiations, so you don't have to take my advice here:
Only two of you are on horses (Talas and Arien). Two other horses are effectively removed from the party now that you are under attack (Dapple and Char's). I will have to check the sheets but unless Jals', Adrian, and Kilgrim's mounts are war trained, they are freaking out about now. You may have a hard time getting pass the Ankheg to run east.
Furthermore, you have four (so far) highly mobile enemies with missile weapons, that look like mantis and dropped in out of the sky. They can probably jump faster than you run.
The Boys are not combat trained and will be freaking out soon (very soon - like now).
btw - Bullrush is a 3e move, not 2e
Now I hate to say never but I would say there are a lot of challenges to face in running.
