I came uncomfortably close at the end myself:
That was with the questline finished and 8 upgrades in my inventory. I was worrying the whole time I was going to run out of tools with something stupid like 1 or 2 idols to go. And I was pretty much focusing on idols during the event. I ended up with 3 leftover idols.
I don't know how much of a random element was involved here. For example did Inno divide the tomb into 8x6 chunks, and assigned a set amount of idols to each chunk, or was there a probability to get iolds every time a new column was uncovered? The first possibility probably would have a better guarantee of a WF with a completed questline, but I have no idea how it was set up. And there's other elements like the tomb layout that had an unknown amount of randomness to it.
But it was still a success. I held onto my tools when I saw some older event buildings made a return in case something like a Checkmate Square came up, but did my digging on the Carousel days and today, Renos are fine for a final prize. I ended up with a full set of WF upgrades, 7 Carousels, got the Indiana Jones avatar on two cities, and I think 8-10 Renos on my main today (I wasn't really counting them).
I think they had set days for the avatars. The last Carousel day I found the Indiana Jones avatar on two seperate cities, like I mentioned above, and I think there was another day when I went for something like WW shrinks on my side cities, I picked up a Delilah avatar on two seperate cities IIRC.