Sounds like you're gonna get to HK Station by 8am at latest, unless your flight's late or you take a very long time at PPL. If that's the case, then no use sticking around IFC/Central until Tim Ho Wan opens (and IFC mall doesn't open till even later). Otherwise, I like tentseller's recs.
Alternative:
When you get to Central, just take a cab and head straight to the Peak Galleria. There, walk the loop around the Peak (Lugard/Harlech Rd). By then it should be ~9.30am. If Mak's Noodle at Peak Galleria is open by then, consider stopping in for wonton noodle. Otherwise, take the Peak Tram down. Then walk through HK Garden over to Admiralty, catch MTR there to cross over to Tsim Sha Tsui. Once in TST, shopping at Harbour City and visit Peninsula (look for gift for your wife at the Peninsula Boutique maybe). Some excellent dim sum in TST, including Spring Moon, Tsui Hang Village, Fook Lam Moon, even Loong Yuen. Then take the Star Ferry back to Central and catch Airport Express back to HKIA. Actually, maybe skip Harbour City and just settle for Peninsula and dim sum in TST, if you want to start heading back towards the airport by 2pm. Highlight will be the Peak, Star Ferry, dim sum and HK Park.
Tim Ho Wan's bbq pork bun is quite good and the outside 'bun' has semi-crispy texture, but Fook Lam Moon's is somewhat similar and even more delicious imo.