Have a pair of short lines for the stern. Long enough to go from a stern cleat to the pontoon and back. When on our home berth a pontoon cleat is adjacent to the stern cleat, so the line in at right angles to the boat. The stern lines are just long enough for this, with a little to spare in case were are visiting and can't quite get square to the pontoon cleat. Very rare we can't get more or less square, on the odd occasion we can't, we use one of the longer lines. We have two so that when approaching a mooring we have lines attached to both stern cleats. Don't always know which side we need them when visiting and i think it's good practice to have both ready and both sides fendered, in case things go pear shaped. This can then be "slipped" from onboard when departing the pontoon.
A pair of bow lines a bit longer, just short of the prop would work OK. I always tie these so they can be slipped from oboard when departing. If the bow cleat is roughly adjacent a pontoon cleat, i usually swap this for the spare stern line, keeps the lines tidy.
Cut the remainder in half.
I don't like running the spring from the bow cleat aft, as the line is against the hull too much. Same with running the stern line forward. We have midships cleats, so i run two spring lines from the midships cleat, fore and aft. These are tied to the pontoon cleats, which only have the spliced eyes from the bow and stern lines over them.
When we leave, we take the springs off, get onboard and slip the bow and stern lines.
Regarding your son being at the bow, i also don't like anyone at the bow. As we have midships cleats, we generally don't bother too much with the bow line initially. We use a stern line and one from the midships cleat to get alongside, then sort out the rest at our leisure. If you don't have midships cleats, i'd have him run a line from the stern back to the cockpit (remembering to keep the line outside of the rails ) As you come alongside, someone gets the stern line and he can step out of the cockpit and leg it along the pontoon with his bow line.
Not wishing to give any egg sucking lessons, but it's handy to know that once the stern line is attached, if things get a little pear shaped or the wind starts to blow the bow off the pontoon, you can just engage forward gear and the boat will stick to the pontoon, no matter what.