Hi...

What would the EPV of an annuity payable continuously to joint lives until 5 years after the second death be?

If I interpreted your question correctly you are looking for a last survivor annuity with a guaranteed annuity payable for five years after the second death. The expression would be:

$$ \bar{a}_\overline{xy} + \bar{A}_\overline{xy} \bar{a}_\overline{5|}$$