Size of dog does not equate the size of smell.
Small dogs piss and shit just as much as big dogs and the smell is the same.
Good Grooming practices and good house keeping (which based on what you have said will not be an issue) maintain things like that.
Im going to go at you with a different angle. Get a dog that YOU want. Not what your child wants- Your child has no clue what breeds are like/do. She has no clue what it takes to go through all the training. All she knows is "cute/fun/puppy" Thats it.
I could hand your daughter 15 different puppies tomorrow and she would pick one based SOLEY on the looks of hte puppy and want every single one of them.
If you want a MinPin, fine get a minpin. But dont let your daughter do the deciding factor of what breed. She has no way of knowing anything about the type of dog she is getting. She wont know untill she's in her 20's when she faced with picking her own breed of dog. She will either look back on the dog she grew up with distaste or extreme joy. She will not say remember when i was 8 and i researched what breed dog i wnated??
What do YOU want out of a dog.
Do you want low grooming? Do you want to deal with fur or hair (brushing vs going to the groomers) double coats?
Do you want a dog who will be easy to train and listen to you when you talk?
Do you want a dog who will challenge you with its cleverness?
Do you want a dog who will be yoru childs best friend?
Do you want a dog who will be mildly, strongly or overtly protective, of house and family?
Do you want a dog that needs an hour of activity a day or will hike 5 miles and still want to wrestle when you get home?
I need to elaborate on a dogs willingess to train vs being smart dog.
Some dogs are just easy to train (this is why Labs are a great go to dog- THey are smart, but not too smart, they want to please you so they will learn quickly) Border Collies/Aussies tend to be Too smart and can be quickly trained but its never enough for how much thier minds work and are easily bored, and can turn destructive.
Both are smart breeds- but its the difference in thier smarts that can be an issue.
(these are just two examples, many dog breeds are like this)
This is a 14 year decision.