Q. (A prior already married couple [to each other] that is now converting and going to the chupa on the same day as the tevila.)Do their children attend the chupa?
 
A. In question 693 on this forum we wrote; “It is customary that children from prior marriages do not attend the Chupa. (Nitey Gavriel 51: 9) Some quote in the name of Horav Eliashuv zt”l that it is out of respect to the divorced or deceased parent.”
Horav Shlomo Miller’s Shlit’a opinion is that this does obviously not apply to a prior married (to each other) couple with children, that now converted and is getting married.
(See also Talmud Sota 12a that Aharon and Miriam danced at the chupa of their parents when they remarried.)
Rabbi A. Bartfeld as revised by Horav Shlomo Miller Shlit”a