First- congratulations. Buying a subsequent home is not a light sacrifice!
Two quick options- you either sell the first home off or let it to a willing tenant. Other options would be you offer it for charity work and so on.
What primarily determines whether to sell off or to continue holding on it is your current financial commitments, probability of your family needing the house in the future and easiness of getting a buyer and sell-off price.
If for example out took a a loan to finance purchase of the second home, you may consider disposing of the fist to clear the current loan. Also, if for example your children are growing and will need the house in the near future, then you may prefer holding on it to selling it off. If you have a ready buyer willing to pay a purchase price that will make a good return to your investment , then you may consider selling.
Other factors may be:
- Location relative to your new home.
- Rent returns that tenants will pay.