If Jefferson and Jackson aren’t considered worthy enough to lend their names to the Democrats’ most important annual dinner because they owned slaves, the logical replacements for them would be the presidents who did the most to free the slaves — Abraham Lincoln and Ulysses S. Grant, who did the most to fight and win the Civil War.
Although Lincoln and Grant were Republicans, an annual Democratic Lincoln-Grant Dinner would be still be appropriate, since it would honor the two presidents most responsible for creating the Democrats’ all-important Black vote, without which they could never win the presidency or most statewide elections.
Dumb idea. It would be stupid and offensive for Republicans to give up Lincoln and Grant to the Democrats, who fought them at every step of the way.
That vote you're complaining about wouldn't be as large as it without Jefferson, Jackson and other pro-slavery Democrats, so the Democrats should probably keep them.