Some postoperative risks that are specifically related to tonsil and/or adenoid surgery include:

Delayed bleeding from the tonsillar area
Although delayed bleeding after tonsillectomy occurs in just a few percent of all patients, it can happen anytime after the procedure.

The most common time frame is during the second week. When bleeding does occur, it is usually because the scab that formed over the incision became infected or fell off too soon.

Most of the time this bleeding is minor, however, there are large blood vessels nearby that can lead to more serious bleeding. If you have any bleeding after you leave the hospital, we recommend that you immediately go to the nearest Emergency Room.

Postoperative infection
As with ANY surgical incision, the tonsillar area can become infected after surgery. Your doctor MAY want to prescribe some antibiotics to help avoid this problem.

Unusual scarring of the soft palate and tissues in the back of the throat.
Scarring in the region of the soft palate and tissues surrounding the adenoid pad occurs in far less than 1% of all patients. Advanced surgical techniques have made this complication very rare. It is correctable with additional surgery. However, these operations are fairly complicated and may require several stages.

Problems sealing the soft palate against the back wall of the throat
Children with extremely large adenoid pads may have some short term problems moving the soft palate after removal of the adenoids. The soft palate may have become a bit "lazy" because the adenoid pad was helping to seal off the back of the nasal cavities during speech and swallowing.

If the seal is weak, children can have temporary changes in speech quality or have fluid leak from the nose when drinking rapidly. Usually time and simple speech exercises are adequate therapy for development of necessary strength and bulk in the muscles of the soft palate, so that it can create a good seal. It's very unlikely that any surgical procedures would be required to lengthen the soft palate itself.