Hi.. for photos, click "more reply options" at bottom of the posting box... browse for your photo, then you have to do two steps once you have browsed for your photo.. click "attach this file" and when your photo shows up as a thumbnail in a separate box under your message box, look to the right of that box and you will see a "add to post" option... and your photo will show up in your message.
Now... for your questions... since you said you are "new to ponies" I am going to ask a super basic question... are you sure the male horses are both stallions? There are some geldings that jump mares when they are in heat. I ask this because I was a bit surprised that the man sent two stallions along to live with a mare pony that was to be a pet for a little girl. I would not ask this question except for your comment about being new to ponies, I am in no way being sarcastic. I used to work for a vet and have explained animal anatomy to many people, the funniest was explaining to a lady that her bunny did not have "tumors", but that she had testicles and she could think about changing "her" name.
I personally don't recommend housing two stallions with one mare all together all the time. Breeders might chime in and have a different opinion, but it isn't something I would do. If I were buying a pony for my child, I would not want the distraction of breeding... and foaling and my child wandering into the field to see her new pony and have the stallion giving her an "education" etc.
Secondly... you have to watch that grass on ponies.. Many can founder easily on unlimited grass. Founder would be a disaster, especially if she is already pregnant. I would have the vet check her for pregnancy, and separate her from the stallions to prevent any more breeding should they be fertile and stallions... I would not wait a month to see if they do it again and take another chance of a breeding.
I have so many questions. I don't want to overwhelm you with a huge posting...
Horses need more than just grass, I give mine a supplement and for my fat boy, he gets remission or quiescence to help prevent founder and a cresty neck.
If she already has a cresty neck and fat pads, you need to act quickly. If my boys had unlimited grazing they would get HUGE in no time and would probably founder. This is true for many small equine but not all..
I hope this helps. Welcome to the forum and welcome to the wonderful world of small horses (or ponies). best wishes.