Hi @thealevan
You should have a Petty Cash account which could be used for your cash takings. Card takings are slightly different because of the fee associated with this.
This topic could be of use to you:
http://community.quickfile.co.uk/t/accounting-for-daily-takings/8911
Although not specific to a mobile bar, the concept should be the same.
If you need further help, please let me know! 