The verb 'provide@

When you're using "to/for" to modify the verb "provide," they are interchangeable. Anything you can "provide to" you can also "provide for" and the meaning will not change.

The difference is small, but it is about inference: If I provide something TO you, then it infers that I am the independent variable - that I choose to provide something TO you at my will, but that I am the guy in charge of this decision. If I provide something FOR you, then the inference is that this is a favor I'm doing for you, or a service I provide. Maybe it's my job to provide such a service - "I provide sanitation services FOR the corporation." There you could say "I provide sanitation services TO the corporation," but the second one puts me back in the throne: it sounds, to a native, as if I am a freelance worker, and I CHOOSE to provide my freelance sanitation services to the corporation. The former one sounds like I am their employee.

The difference is very small, and it will not change the direct meaning, so if you're not comfortable here, do not let it worry you.

*NB: if you use "to/for" to modify OTHER verbs, the meanings can begin to differ. EX:

1. "I delivered the meal TO you as promised." Very cold and un-friendly usage. I could be a prison guard. I was only meeting obligations.
2. "I delivered the meal FOR you as promised." Maybe I'm a waiter, and patiently hoping for a tip! =)

EDIT: I just saw your specific examples... What a less-than-careful reader I was..

1. 'They provided enough tables and chairs for the guests' = The inference is that "they" work for the good of the guests. Maybe they are waiters or hotel employees, for instance. It's clear that this is a thing of service or kindness that is being done, and the guests are meant to benefit.
VS
'They provided enough tables and chairs TO the guests' = The inference is that the tables and chairs were enough in number. It does NOT say that they were cleaned, placed correctly, and dressed for the benefit of the guests; rather, it INFERS, that they were simply 'made available' to them. (A good example of this can be found in American legal language, the sort you might find in a contract. A statute might give a time limit of 6 months, to file a grievance. When the 6 months had passed, a notification of this might be phrased: "A period of 6 months was provided TO you to file any grievances, and since you have not done so, the statute has expired and the motion is final." As you can see, it was not friendly, and it was not a service or a favor to you. It was simply 'provided to' you.)
'They provided excellent service TO the guests.' = Because you clearly said "excellent service" here, the inference is killed, and this means the exact same thing as 'They provided excellent service FOR the guests.'