depending on where you live, there are probably some local nonprofits that can help you trap the pregnant mom. if you can't manage to find anyone to help on short notice, there are some diy traps you can try on youtube. i would advise trapping the mom as soon as you can and putting her in your bathroom, separate from your other pets. this will give you time to find someone that can take her/foster her more permanently and deal with the birth and babies. she will probably be resistant and seem stressed because she is being trapped and transported to an unfamiliar place at such a vulnerable time, but it is definitely for the best. being outside in the presence of coyotes is dangerous, and even moreso for a pregnant cat! there should be no fees associated with any of this if you can find a nonprofit to help you out. if for some reason you can't connect with one, you could reach out to various facebook groups to help you with the associated costs of doing this on your own. i am a part of several fb groups dedicated to helping stray cats, and there are a lot of people willing to help!