Congrats queen of tarts on your engagement
Don't know your whole situation but it sounds like you both have kids? I'm assuming his kids are currently living in the house with his ex?
If so this opens up more situations to think of such as his children's views on you and their dad living in the family home, who would get which bedrooms (your kids, his kids,etc).
If it were the two of you you could gut the house and do it all up as your own but the kids will always view it (rightly) as their house and may resent you for it.
I'm not saying don't go for it but it is something else to bear in mind while you are making the decision.