First kid - that's a significant milestone and probably one he!! of a lot more important to you in the long run than reloading.
Theoretical dangers from chemical vapours from propellent and such are essentially non-existant unless she's stuffed her pillow with the stuff. They can be safely ignored.
Danger from lead (and other heavy metals) is less theoretical. The human body needs zinc, sodium, carbon, oxygen and a lot of other things - but we need not one single atom of lead. Basically, the less lead in us, the better. There are theoretical tolerable limits on lead exposure and that's good, but what they mean is that, for most people, under normal situations, this amount of lead won't do enough harm to be noticed. Now compare that to your stituation, involving a woman you love and your first-born kid. Maybe the theoretical doses are still applicable, maybe you want to play it completely safe. I certainly wouldn't fault you for being overly cautious. It's like drinking; most women can probably have the odd glass of wine when pregnant without risking any fetal damage, but many if not most choose not to risk it.
Personally, unless I was shooting a lot, I'd think it would be enough to just minimize an already low risk - stop dry tumbling, vacuum a lot using HEPA filters, wash hands and clothes a lot, close off the return or cold air duct for your reloading room and so forth. BUT - it's your kid-to-be and anybody calling you a twit for being concerned probably reproduces by binary fission. The only people with a right to call it are your and your wife.
Oh, BTW, congratualtions, Dad! There's no feeling in the world like holding your first-born in your arms. Good luck to you three.