4 Aventura Points may be converted to Aeroplan Miles at an exchange rate of 1 for 1. Points must be converted in 10,000 point increments. To convert points, your CIBC Aventura World MasterCard Card Account must be in good standing.
Based on the above you'll either need to do some charging to get another 5000 points so you can transfer 20K to Aeroplan, or blow off 5000 points.