If i don't care abt the shop CE, can I just exchange for choco

This is more or less the conclusion I came to myself just yesterday. If you have, say, a full party of the gacha 5* ce's from pulling for MHXA then you're much better off popping a mold each time and farming for a single coin (doesn't really matter which coin) and then turning them all into chocolate.

The farming this way is actually pretty fast and this event is long, so you might find yourself with lots of leftovers at the end to get the ces anyway and maybe even get some of the servant ces for collection purposes.

Yeah, you could do that. And like chairman said, the event is long enough that you'll have a lot of time and chocolate/coins leftover. If nothing else, the shop CEs are make good exp feed for CE Bombs. Each one gives 30k exp.