Fostering is a great idea and many congratulations on wanting to do it.
Most rescues are absolutely delighted when families are available to do fostering, as it enables dogs to then go to family homes with DC experience under their belts, so to speak.
The rescue will have a chat with you about the support you'll be offered. You should have access at all times to a foster co-ordinator who you can discuss any concerns with. Initially, at least, I'd expect them to place dogs that have previously been in a home with you. These can come back to rescue for instance if their owner dies, or as an owner surrender (typically, divorce, emigration etc) and a dog that's not used to kennel life or an oldie especially would go to a foster home in preference.
I'd expect the rescue to discuss ground rules around how you and your DC interact with the dog - this is NOT trying to interfere with your parenting but is trying to ensure safe, happy co-existence between DC and hound. For instance, I'd expect you to ensure that dog is never disturbed when sleeping or eating (and make sure DC know about greys sleeping with eyes open), and that it might be a good idea to have baby gates to allow separation of dogs/DC for everyone's safety.
Crate usage might also be an option to allow hound to have designated safe space that is out of bounds to DC.
To be honest, if your parenting style tends to the very crunchy/"my darlings are spirited" then this might not be right for you - I don't think it's fair on any dog to inflict noisy, grabby toddlers who are never given boundaries (hasten to add this may not be your parenting style).
Other things to think about - walks - will you walk dog plus toddler in buggy? Or are you expecting to do dog walks separately from DC?
Car travel - do you have a secure boot, preferably with boot guard? Will you be able to take foster dog to any necessary vet appointments, and will you be willing to follow guidance on basic training (e.g. whistle recall) and/or take foster to training classes?
Biggest danger - you will fall in love and join the "failed fosters club" - quite a few of us are proud members of that.
Good luck!