I am not one for cutting it fine, so I would personally allow 15-20 minutes from parking to the place. I allow 45+ mins from leaving home at Windsor Palms to the rope drop at MK - this gives plenty of time for any delays (e.g. if we don't make it out dead on time - sometimes takes longer to get out the door than expected), packing things up for the trams etc and we are usually there with 10 mins to spare (told you I don't like cutting things fine!) and no stress.
If you can and the lines are not long, take the monorail over. But if the boat is there and you have time, its a nice journey (especially early in the morning when the boat is not packed).
If you are early and parked close to the TTC, you can walk to the entrance rather than taking the trams. We do that often - it saves time and hassle (usually we have had a stroller with us)
If you have to purchase entrance tickets, allow extra time for that.
Others may suggest shorter times, but I know in my family's experience I would rather have that extra time and not be stressed out on vacation.
HTH