Shelly, there really is no risk associated with using tires with a heavier load rating. It might mean that they'll be more expensive (since it's a good feature), but really it just gives you more headroom in terms of towing capacity.
The most important rating to me is the tread wear rating, and for standard tires on standard cars (as opposed to race tires for race cars), the higher the number the better. There is some variance from company to company, because each manufacturer is allowed to establish their own baseline performance, but the rating ranges are typically 100 to 600 (although there technically is no upper limit). Effectively, a tire with a 200 tread wear rating will last twice as long as a tire by the same manufacturer with a 100 rating. Ratings of 400 and higher are definitely "good" tires in terms of their expected lifetime performance/mileage. The only downside to high tread wear ratings is the slightly higher stopping distance. The higher the tread wear rating, the harder the tire, thus the less sticky and thus the lower the friction coefficient. You might enjoy the math... http://en.wikipedia.org/wiki/Treadwear_rating
Anyway, the higher load rating on the tire you're considering is definitely a good thing. But at least check the tread wear rating to see how it compares to the originals that you're replacing. Michelin to Michelin means that those ratings will be directly comparable.
There are other measures besides the load rating and tread wear rating that tires are rated on, like the temperature range and speed rating (which is alphabetical), but I've never found these to be particularly important unless you're planning to drive a lot in the desert or over 113 miles per hour. You can run a 102 mph rated tire at 140 mph, but you wouldn't want to do it for long!