There are several ways of doing "memorials" at your wedding.
First, you could place a large pillar candle at the entrance to the ceremony, on the table with the Guest Book. You can light it before the guests arrive, and have a small card in front of it that reads "In Memory of _______ (Name)". At the beginning of your ceremony, the Officiant can pause and give an explanation of the "Memorial" candle. _______________ (Name) may not be physically here with us today, but they are looking down on us and are here in spirit to bless this union. ______ (Bride and/or Groom) has lit a candle at the entrance in memory of __________ (Name)."
Or, you could do the "Memorial" at the beginning of the ceremony. Have one or more tall large pillar candle's), in a color other than white, on the altar or table (on either side of the Unity Candle). With special music playing in the background, you (Bride and/or Groom) would walk to each candle and light the candle (you could use your small tapers and the votive candle), then you two would walk back to your positions in front of the Officiant. While the music is playing and you two are lighting the candles, the Officiant should explain "_______ (Name) may not be physically here with us today, but they are looking down on us and are here in spirit to bless this union. ______ (Bride and/or Groom) will light a candle in memory of __________ (Name)."
Another option is to place a Poem or Reading dedicated to the "absent" person in your Wedding Program (In Memory of ...).