I would definitely accept first and then not necessarily set out to tell anyone straight away, but not try to hide it either. I'm sure there will be opportunities where you can casually mention it without making it a 'formal' announcement or declaration.
I applied for a job when I was 3 months pregnant and didn't tell anyone at the interview or orientation. I had to tell one woman that was giving me grief about wardrobe because I had to start wearing maternity pants that I couldn't find in the same 'acceptable' style, but I still didn't make it public. I waited until I was legally required to tell them that I'd be going on mat leave (I think it was like 12 weeks before date of leave starts).
I was on probation the entire time I worked there before I left for maternity leave and I didn't want to chance it. One of my best friends told her employers that she was pregnant while she was on probation and they had found some BS excuse to let her go within a week of her telling them.
If you're not legally required to disclose the information and you're not lying if someone specifically asks, then I don't think there's anything immoral about it at all. You can't always trust that your employer is going to behave ethically, especially at a new job where you're on probation and letting you go is easier, so I think the most important thing is protecting yourself.