Rehearsal Dinner- formal or informal!

We are doing a formal dinner, because our families have never met. You should definitely not have any cook for your RD.

Cooking in some families is a tradition and I think that cooking the cultural foods will be great because then everyone can talk about it and mingle about that! Food is almost always a comfort zone for everyone.

We're doing something similar. Our wedding will be super formal so we wanted our RH to be more casual. FH's parents rented a large home (that they will stay in for the weekend) and we are planning a backyard bbq style rehearsal dinner - catered bbq with servers, self serve bar, lawn games, cards, dominoes, etc.

I love your idea of renting a house and keeping it casual, but like @Kate said, the RD is to thank people for rehearsing, and asking them to cook as their thank you does not really work. I'd consider ordering some food in. We are having pizza delivered from a local restaurant for ours.

This case may be an exception since in some cultures, it would be insulting to not let people cook. It might seem offensive to ask someone to cook at your RD or wedding in the US, but could be a different situation elsewhere and that needs to be respected. Of course, OP knows that best.

As far as OPs question goes, either formal or informal is fine. What you're doing sounds wonderful. We are having a catered open house at our house the night before. There is no rehearsal so it's really for OOT guests and relatives. We're catering from a local Jewish deli which for our crowd, will be a big hit.