Congratulations on getting a new mare!
May I ask what you intend to do with her. If she has had that amount of foals, is pregnant again and feeding a foal now, she will need a few years rest to get herself back into shape I would think (she deserves it too!)
I have no idea about the feed available to you in Canada, but it seems Chanda has already given you help in that direction. Will you be able to turn her out to grass? As she has already been used to grass then her system wont be used to anything else so to change away from this to 'dry' feed and hay may cause her a problem. Can she graze and you suppliment with her new feed and give hay as required?
As the foal is now 2 months old it will be quite safe to worm both her and the foal with a good wormer - dont use Quest on mini horses - then perhaps get a worm count done by your vet a few weeks later just to check. I think it will be quite a while before you can think about possibly reducing the size of her tummy, after all those foals she is going to stay pretty extended whatever you do, but anyway you will have to wait until the foal she is expecting is weaned.
I dont know how far she and her baby will be travelling to get to you, but on arrival it would be better to turn them both out in a grass paddock (not lush) as this is what she is used to, than shut her in a stall/barn and feed dry hay to a system that is already compromised by the journey. Just my opinion.
Good luck, cant wait to see the pictures!