Even with combined assets and/or in a community property state, you will need separate wills, each controlling 50% of your assets.
Our wills each address the following scenarios:
First of us dies: the surviving spouse (or named SO) gets everything.
Surviving spouse dies: our now adult son gets everything. If he is not living, then our estate is handled as if both of us died together. In the future, we may revise this to name him and our respective other bequests (see both die together).
When our son was a minor, our wills named a series of guardians and financial trustees (not the same people), in case the first could not serve, and created a trust to manage his inheritance and compensate his guardian if both of us were deceased.
Both die together (within 30 days): each of us has designated our own beneficiaries for our 50% of the estate if our son is not living. These are named relatives, friends, and charities, usually by a percentage of our bequest, not a specific dollar amount. If a relative is not living, we have chosen to direct that person's share to his/her descendants if living.
Our wills essentially are the same, with the exception of the individual preferences for beneficiaries. Our executors are 1) each other, 2) our son, 3) an independent financial institution; #2 or #3 serve if #1 cannot, thus the surviving spouse still has a valid executor specified when the first dies. We also followed this serial designation for springing powers of attorney for health & financial affairs decisions.