If I may offer a suggestion for the number of tinies... and this is coming from someone who has no experience or knowledge in game construction...
But this issue reminds me of a little flash game on Deviantart involving a lady destroying cities. You can control her size, and after a certain point, people are too small to be seen, so maybe make it so that they're there but you can't see them. Basically a check in the game's coding where every step crushes X amount of tinies.
Or, an alternative, which may be easier or harder, maybe once you grow too large to see them, just make it so that every step squishes a random amount. Like no checks or coding, just every step causes between 100 to 300 tiny squishes.
Just a couple ideas coming from a person who has no idea what they're talking about.
Viewing post in SNS Macro March Playtest | FAQ & Highlights comments
Ah, I get where you are trying to go with this!
We actually had a fun idea to add a bonus level transition. If you manage to do well during your playtime, possibly a simple cutscene plays, showing the giantess growing, white clouds fading in, while the new size map is loading. After that, you would get your giga play size! X3
We wouldn't have to worry about seeing the tinies on screen, as you pointed out that they would be too small to see. :3
Ah! A delightful idea! I had another this morning and that was they just weren't on the map at all and instead hiding in buildings or driving in cars. You know... the logical thing when there's a giant girl growing larger and crushing everything around her? Trying to escape or hide? XD
I like your idea more though. Looking forward to more! Good luck and have fun as well.