Hi, we're in a similar(ish) situation, however we dont have any kids just yet. My wife (35) was diagnosed with BC exactly two months after getting married in Feb of this year. Where as we were hoping to begin trying for a family, instead she underwent a mastectomy and we're about to begin 16 weeks of chemo. Its not how we planned on starting married life. As part of the process, we were offered IVF on the nhs, which we took and have stored embryos for future use. My wife's BC was ER+, so she will have to have tamoxifen.

The rule (as far as i'm aware) is you need to stay of tamoixifen for between 5-10 years, however, you are allowed breaks in the process to concieve. I would speak with your care team, and they will come up with a plan for you. We have found that there is a specialist team within the nhs who deal with this situation and can advise. Dependant on the situation, they will put you on tamoxifen for a set period, then begin to flush the drug out of you to ensure youre free of it. You will then have a set period to concieve. 

The good news is, having a break for a baby does not increase your chance of a reoccurrence,

Good luck in the future and I hope your recovery goes well.