Best way to get from Hong Kong Disneyland to Ocean Terminal

If I take the MTR, and (taxi?) how long vs just taxi which may take longer 'cause of traffic?

Was thinking of leaving at 7:30, so can see fireworks when leaving, ship departs at 11 PM.

Harbor firework is nightly @ 8PM, weather permitting (check forecast !!) and I would go MTR leaving DL no later than 7 PM, allow time for walking from TST's station out to waterfront/promenade to get a good photo spot a few minutes early (or, back onto your ship's upper/outdoor deck, depending on which side it's docked (Star Ferry side facing Wanchai is good, facing West Kowloon - not so much) MTR with the transfer is predictable even though trains will be crowded and still evening's rush hour for locals. Taxi trip is about 22 km + and travel time is 25 minutes, excluding traffic which you can definitely count on & add to, metered fare per vehicle will be about $300 +/- HKD or $40 USD w. small driver's tip included, payable in local currency as mobile credit card payment terminal is often out-of-order ;)

You will miss the fireworks leaving Disney at 7:30 either way, enjoy your stay.