Under JAA, after finishing exams it was 18 month to do the CPL and 36 months to complete the IR, I don't think EASA have changed this? you wont be able to save for three years for the IR as your exam credits will expire. However you could do a Single Engine IR by the compentency based IR route at a lower expense to preserve your exam credits and then upgrade it later to a Multi IR later on. I would recommend for the CPL to try and take a month off to finish it, doing it part time will drag it out and more than likely you will end up doing more hours to complete it. Plus don't under estimate trying to do training along side your busy schedule.
The other thing to consider is getting your first flying job will involve relocating and / or staying away. It isn't easy to uproot children for a short time and first officer pay is rarely enough to pay mortgage in one location and rent in another. Completing the training was not the difficult part, finding a job not as such the difficult part either. Getting a job that pays enough and fits with family life, that is tricky.
Good luck; btw self employed security work can fit well around part time flight instructing. The other thing to consider is you could do CPL-FI, start instructing and building hours before doing your IR.