Flagged US resident crossing for two weeks...Advice?

I am flagged for risk of over stay. I recently crossed at the end of March with my two children and I think I only got across because my partner was with me. This time I am crossing again after being in the US from July to the end of October. I have a job now where as in the past I did not.

I will be crossing with:
A letter from my employer stating I have two weeks off
A letter from the children's father stating the girls can stay for two weeks in canada ( I have full custody in divorce but my papers also grant immigration so I do not want them to see that)
Travel insurance for the girls and I during our stay in Canada (this was the issue last time that the IO came up with)
A return hotel booking outside Chicago which will be half way from Toronto when we drive home
My reason for going is to see boyfriend and do Halloween with him and the children

Do you think this will be enough? I have visited four times in the past 18 months and always returned also so hopefully my past history will work in my favor.