It depends on where you live. Some states require disclosure -- others do not. (There are probably many more deaths in homes than anyone ever know about.) If the death in the home was or was not a brutal event -- the neighbors would surely tell the new owners anyways.
You're ready for a bigger home, but you're stuck in a catch-22. If you sell first, you might end up scrambling to find temporary housing while your family lives out of boxes. If you buy first, you could be stuck carrying two mortgages while your current home sits on the market longer than expected.
Meanwhile, the market does not wait for you to