I'm not a PA attorney but I am a PA title agent and if this transaction came into my office here's how I'd look at it:

In PA martial property only applies if the parties are separated or divorced.  If they were still married at the time of his death then the property is owned soley by the wife, period.  If you're really concerned, get the wife to sign an Affidavit of Continuous Marriage.

For the fun of it, I'll take it a step further.  Had this been a situation where husband and wife were on title, then the property would pass soley to the wife because we are a tenants by the entirety state.  So even in that senario, the children still don't have any right to the property until the wife dies.