I moved a lot when I was a kid, and it hasn't hurt me at all. I went to 3 different school in 2nd grade, that's how much we moved! It sounds like your fiancee has a great house for all of you in a great neighborhood. Your mom probably just likes the situation as it is, and doesn't want you and the kids to move and is projecting it onto the kids, instead of being honest and saying "I want you guys to stay here." 25 minutes is really nothing. Your mom will still be able to see the kids on a weekly basis, go to their school events, see baseball game, etc...
I don't think this is true eaither. One, selling and buying a house is no small matter. It isn't like buying a new pair of shoes, or even a car.
My husband moved into my townhouse after we got married, and we haven't had any problems with it at all. You're saying I was supposed to sell my house (that I've only lived in for 3 years) because I was marrying someone? Technically, the mortgage is in my name only, but we always refer to it as "our home."
I know your "guy" loves the house but it is ALWAYS best to start a relationship in a house that belongs to everyone. Get a new house if you can.
Our friend just married and they moved into his house & it has caused lots of problems
I don't think this is true eaither. One, selling and buying a house is no small matter. It isn't like buying a new pair of shoes, or even a car.
My husband moved into my townhouse after we got married, and we haven't had any problems with it at all. You're saying I was supposed to sell my house (that I've only lived in for 3 years) because I was marrying someone? Technically, the mortgage is in my name only, but we always refer to it as "our home."
He just recently refinanced his house, so asking him to sell it to move to my home town doesnt seem quite right, plus he loves the house, its an older house that he has spent a lot of time restoring and its so perfect, I love it's charm and beauty. So, my dilemma is, would you move your kids to a new home/new school because of marriage/love? Whats a girl to do?
People move their kids all the time. I could see if you were going to join the gypsy life and move every year or so. But moving 25 miles away is NOT a big deal(what is that 35 minutes?) Are your parents enmeshed with your family? In other words, do you think perhaps your mother doesn't want you to move for her own selfish reasons? Or are you just a mama's girl. When people get married they cleave to one another. Mom & Dad and their opinions move to last place. 
I'm a single mom who lives with my parents and my mom has told me flat out that if I get re-married, I will have to leave my daughter with her. How's that for paranoia?
Your mom is speaking from fear. They fear for their grandbabies in a new environment. Its totally irrational but rational at the same time. Its a paradox. My advice: live your life and move forward. Assure your mom that her place is still important in your lives and that you will do your best to make everyone happy.