Oh yes, plantwise - I've got one plant in my tank that the fry love. Sadly I've got no idea what it's called, but it's got long brush like needle stems that the fry can squeeze in between when a predator is around. I'm sure someone else can recommend a plant by name, but I would have thought that any dense growing plant with lots of stems would do the job.
I think I paid £1.50 for it a month ago and it's now probably 4 times its original size.
I've found that after about 10 days the adult guppies don't attempt to eat the fry anyway, but I don't know much about mollies.
I think some people put live moss on, which is also very good, but I don't think it grows very quickly.
Kathryn