You could either store the word graph as a partitioned set of S3 buckets, or have a back-end that serves individual words and does rate-limiting. I guess that the back-end might be better to avoid surprise egress charges from anyone trying to download the entire dataset.

I want to try out the game but I'm discouraged by the download size.

We use the top google Ngrams in 2 ways. (a) we share it in the reference mode of our app, i.e. common words before or after; (b) we use longer N-grams, where possible, like a 4-gram, to choose literary examples that also show a common pattern.