CIC tends to issue applicants with your profile a Residence Questionnaire (RQ) that will require you to provide documentary evidence of your presence in Canada in the 5 year period under review. You need to provide proof of 'active' presence which means anything that requires you to be physically in Canada. Such proof includes any medical type billing such as dentists, opticians etc. Most applicants apply to the Provincial Health Ministry e.g. OHIP in Ontario for a billing record which is what medical professionals bill the province for providing you a service. Passive proof e.g bank statements are usually disregarded or only considered as supplementary data e.g for employment pay. Submit also any leases, insurance documentation, Notice Of Assessments etc but again these are all passive evidence as you can have them without being in Canada - if this all you have then its better than nothing.
Do you volunteer anywhere? If yes get a letter from someone respectable with the organization to detail your activities. The letter must provide the times you went e.g twice a week from date a to date b.
You will also give consent to CIC to get record of your entries into Canada from CBSA. CIC will expect you to get records of all entries and exits from your passport issuing country and/ or any other 3rd country you may have traveled to e.g US. You have to contact their border management organization e.g for the US its CBP to get these records. These organizations often have back logs so you may want to start applying now.
Submit evidence too of your kids presence - presumably they have the same shortfall in days. CIC will need some info (not necessary documentation) about the other parent unless this was covered at PR issuance stage e.g. they are in your sole custody.
CIC may also in addition to the RQ decide to interview you.
The burden of proof for residence is on you so if you can't convince CIC then no renewal.
