Concerning Willow, since she could be approx. seven months, you van sometimes feel the baby. Do this after she starts eating. Wrap your hands around her belly right in front of her milk bag. Usually, but not always, you can start to feel kicks and bumps from foals. Both of my mares I felt movement around five mpnths along and they now have babies at side. Since she could be around seven months, you can watch her stomach (flank and lower in front of bag). You have to be patient and you may see movement. Works better if she is standing around resting.
Concerning Snicka and Texas. If you have an area that you can take her next to the other minis, that would be great. That lets the other minis see bany but can't rush mom. Mom running from other horses or kicking could get baby hurt. In my option, I would never let the two out with the two colts. If they are still studs, especially Kevin. He's going to want to bred Snicka and baby will get hurt.
We have three stallions and a yearling colt. The two older stallions wouldn't go out of their way to hurt bany, but hormones take over. They rear, strike out (front and back), if baby is in way; whammo. Our third stallion, we've had since a weanling, but he conpletely lets his testicles control him during breeding season. He wants to mount everything, even his new daughter. The yearling just plays ruff and is starting to figure out he is a boy. You can slowly introduce Willow to mom and baby.
You can start putting a halter on in a controlled environment . Stay out with her and never leave her unattended. Leave the halter on for longer periods, but never leave it on when your gone. When the halter goesnt bother he'd, put a lead on. Lead Snicka around have her follow. Don't drag her and if she pulls back, release the pressure until she moves forward again. We don't start asking our babies to lead and tie until they are at least a month old. It works out for the most part, because our babies are handled from birth. Temperament says a lot too. Our four week old filly should be easy, she already follows us around everywhere (even without mom). The new colt, we have to wait and see; but I think he's going to give us a run for your money. He's been fiesty from hour one, probably why is registered name is going to be Ready to Rumble.