How large is the solar panel you'll be using? Or is the term solar tracker used just to mean you'll be tracking a bright light? Reason for asking is I don't know how much torque that gimbal will give you for turning any decent sized panel. Also, if you're only turning the gimbal toward the point where it receives the most power from the solar panel the additional sensors on that gimbal are probably overkill...but still very cool.
From the logging perspective I've got a few of these EEPROMs myself but found quickly that an SD card has a far greater capacity. So far when the internal EEPROM of the ATmega is insufficient the SD is the next port of call so these have gone unused. Of course it will depend on how many bytes each data point will require, how frequent those data points are recorded and the duration of your recording whether you'll need the extra storage of SD but it's potentially worth considering.