I remember the castle play! Hope it went well.
As for your dining scene, you have to write the scene that best serves your play and if that is a dining scene round a table so be it. Lots of plays have similar scenes and for good reason. I can think of half a dozen plays I have seen over the last 18 months that had people sitting round tables eating.
Whatever best serves your play is the scene you should be writing and if that dining table scene has the movement and life you've described it isn't a problem.
When readers look at plays for production and development they know they can fix directions and settings, the wrong format won't kill your play's chances, great dialogue, engaging characters and a compelling story that can be told in an interesting way on stage is what will sell it.
Remember that white space is your friend. Leaving enough space between your lines for everyone else to do their job. And yes, getting that balance right between overwriting and underwriting is hard but that's why plays take so long to be put on from commission. There's always a good lengthy development process and a few more rewrites (with guidance) because you're not even expected to get it right on your own, the first time. Being a playwright is great because you get to play, test, try out ideas and your writing and ideas with others to make it work, often over several months before rehearsals even start.
You need to show you can write sparky dialogue, complex characters and tell an interesting layered story. Everything else can and will be found later.