You may also wish to consider the effects of larger oceans on the planet's heat retention. Water tends to absorb heat, so having a higher percentage of water on the surface will increase the planet's retention of heat, and thus its ambient temperature. On the other hand, it will also produce more cloud cover, which might have the effect of reflecting more radiation into space before it has a chance to be absorbed by the surface. Some research on the term albedo might yield some useful information.