Well 4, I cook for dinner parties & Do's for anything up tp 150 people. It is not a problem once you get your head round it. But I would not use a base sauce as described on the Forum for this as you can not really get near BIR style unless you cook each portion individually. So I would go for the following approach.
Think traditional and cook traditional
You will probably find that most people will go for hot even though in a restaurant they would not choose it (fear of the unknown). But maybe make two (it does not take that much more effort)
Cook bulk, Make a simple onion base to work from.
Make a little Bargar base to start with.
Use curry paste not powders (Ferns or Simtom are the best for bulk cooking).
Use lots of tomatoes pulped
Use fresh ingredients where possible.
Prepare in advance by cooking the curry until the meat is nearly cooked and remove from heat.
Reheat slowly just before you are ready to serve.
Don't bother with Garam Masala, but do use plenty of Coriander for garnish.
Keep the salt and sugar levels to medium (they increase their flavour properties after time)
If the dish is a bit bland before you serve add some lemon or tomato juice to release the remaining flavours.
You can't suit the masses :

If you get it wrong about 20% will eat it; if you get it right 70% will eat it; if it is superb they will be back for more. We usually make enough for 80% of the invited guests if there is more than 50, but if there is only 20 then make 100% plus a couple extra.
Allow slightly less meat weight per portion if it is buffet style.
If it is buffet style don't put it all out at the same time.
Label the dishes - 'NOT HOT' and 'A little Hotter'.
Put plenty of Raita out and explain what it is for - cooling down the chillis.
Put out some sweet mango chutney, and some chilli pickle!
If you want a recipe or two that will work I can email or PM you.
Good luck
Jon