How do you mean they interfere?? You can set up different profiles for each device and you can have different menu items for each device. The profile for the Register can be set up to manage food and beverage service. The Handheld can have a profile that is simple, straightforward to sell items. For example... Your Square Register - which you are using for your bar would maybe have different categories for different beverages and/or food and can be on one side of your menu screen. You can set up the Handheld to perhaps have a button for a charge to attend an event or utilize the keypad to sell items.
They can both be used separately or simultaneously without interfering with each other and reports at the end of the day can show which device collected what amounts of money. Your credit cards will all go to the same account but you can still see the reports on both devices or logging in to the "back door" on your computer.
Shout if you have any additional questions.
