The command does not work because your bash profile isn't loaded when running the first command. Your second bash runs a separate shell, which is probably not what you want.
Mikhail's answer works, but you need to separately find the absolute URL for each command you want to run.
What's needed is running a command in a bash login shell, and then giving the control back to the user. From https://stackoverflow.com/questions/7120426/how-to-invoke-bash-run-commands-inside-the-new-shell-and-then-give-control-bacStackOverflow :
bash --rcfile <(echo '. ~/.bashrc; yarn dev')
bash --rcfile <(echo '. ~/.bashrc; yarn dev')