Another "serverless cron" option from aws is their Data Pipeline service. It is intended for data processing as its name implies but does fits the bill for lots use cases as a generic "serverless cron". Note that Lambda has executing time limit that's pretty short, while data pipeline can be configured to have much longer timeout.
Lambda is already limited enough when it comes to how you can write the functions. I'm not even sure how you'd write a generic JS/Python/Java function on DPL, unless its got some functionality which I'm not aware of (through a custom shell command bootstrapping your language environment maybe?).
