Guidance needed in setting up a timing system

True - but in the end whether solution is best depends on the actual application OP has for it, how the cards are used, etc.

I always find the lack of user interface (beyond the standard Serial, which is not even present in most ATtinys) the hardest part of dealing with Arduinos and related embedded devices, especially when it comes to inputting larger amounts of data, such as this timing table.