What Causes Difficulty In Pronouncing Certain Words Post Tonsillectomy?

hello, my son was born with soft cleft palate and was repaied when he was 16 months and had to have numerous eustatian tubes due to middle ear fluid and eustasian tube dysfunction, he is almost 8 and has very bad sleep aponea , therfore had to have partial adenoid removal and tonsilectomy. its 2 weeks post op, his speech sounds little more nasly and high pitch and water is coming of his nose when he drinks water ever now and again. The surgeon said he would only take out a little bit of the adenoid so his speech won t be affected due to the soft cleft palate repair, however it was so enlarged and he took out about 30% of his adnoid. he is no longer snooring however, i m so worried about his speach that sounds little nasly and hard for him to pronouse certain words clearly ( he spoke perfectly prior to this) and also worried about the fluid coming out of his nose. he has never had tonsilities and did not have large tonsils but the surgeon and sleep dr. decided it may help with his aponea? please help? will his voice ever return to normal?