Using Chickytutor.com for conversation practice before meeting my Czech relatives

I’m a heritage learner trying to shake off the 'foreigner' accent and awkward grammar when speaking with my family in Prague. I want to build more confidence before my next trip, so I’ve been using Chickytutor.com to simulate real conversations and get instant corrections on my case endings. Is it better to focus on formal grammar or should I lean into the informal 'obecná čeština' variants they actually speak?