You had a sudden thought and let out a loud thought announcement "Everyone bring out the corpses of all the people who had died and haven't been reanimated to the main square! Your reanimated bodies should last for awhile but theirs will not!" Concerned a lot of the undead brought out corpses of several people who had hid and were scared. Most of them were kids teens and young adults.
One undead asked "So are you going to cast some spell to bring them back or some special burial or preservation magic?"
You thought out to the crowd "Their souls are already to far for me to find, and if this was just about burying them we'd have time. I suppose it would be better to bury them while they aren't rotten but that isn't what we're doing. A lot of you have fairly old or really young bodies. All that an undead needs is a body and a soul so... If the elderly or really young or infants would like a fit body not in use then... Well why be stuck for eternity in a body that will never age or will only rot faster."
One old undead who was an old lady went towards one of the corpses of an older teen and said "This was my granddaughter. I feel sad about this but we looked much alike when we were young. I feel in this way we both will still live. Would you put my soul in this child's body?" You made a small gesture and the old lady's body went limp as the young teen's body started to move. The body of the teen said "I can't say I feel much but thank you." she then took her old body and said "I suppose i'll put my old body in a separate group. I'd doubt that anyone would want to be in it."
Then more undead came up wanting a body that wasn't a child's or an elderly man's You then got teens and adults playing together like children for awhile, and then young teens acting like wise old people. You thought that your dad would like this better an undead horde that had fewer really young children and elderly.