I²C interface between 3V/5V sensor and a 2.4V MCU
This should work but there are a couple of things to watch:

First, the maximum voltage you can operate the temperature sensor at, for guaranteed I2C operation is 3.4V for interface operation at 2.4V



That is necessary to always meet the \$V_{ih}\$ specification of 0.7Vdd. 

The maximum pull-up resistance depends on the speed at which you intend to operate the interface and you can go slower with larger values resistance. Smaller gulps of current generally tends to increase battery life if only by a very small amount; how much of an issue that is for you I do not know.