Creating booking system for items
Assuming this is about D7, here is a blueprint of just another idea (as in your bullet item "4"):


Create a single node for each number, of content type (say "Golden Coin"), so  10x10 = 100 of such nodes.
Use the Views module to display a 10x10 grid of those 100 nodes, and link each of them to there corresponding node.
Use the Flag module for authorized users to "flag" such nodes, to indicate "reserve this one".
Use the Rules module to make the remaining magic happen, using Rules Events such as "When such node is flagged", with Rules Actions such as "Create appropriate notifications (eg towards the admin)".
Repeat the above for "Silver Coin", or add an extra field to the Flag you'll be using, to select between "Silver" and "Gold".