Adopted a milk goat....now what?

We adopted a doe (about 5 years old) and her two bucklings (not wethered), now 9 months old. We've had them for about a month. Mom and kids had been together on a regular basis but the previous owner claimed there was no sexual activity.

How can we tell for sure?

Hannah (the doe) gives about 1 1/2 quarts of milk every other day. We don't want to dry her off if she's not pregnant but we want her to be as strong and healthy as possible if she is likely to kid. I figured that the latest she might kid, if she was pregnant when we got her, would be early April. I have no idea what the earliest is she might kid.

She hasn't shown any signs of heat since we've gotten her, but I couldn't swear to that as I'm not really sure what to look for. Based on just reading and no experience she doesn't seem to have come into heat. Is that perhaps an indication that she might already be pregnant?

We're new at this (as you can probably tell!) and want to do what's best for Hannah. BTW, the boys will be butchered later in the month (the earliest date we could book it for) and are kept separate from Hannah.

Any suggestions for us? Thanks.
Elizabeth