Public transport in Cambridge isn't terribly reliable, in part because the roads are very congested, but also because Stagecoach can't figure out how to get people on and off buses quickly. They are currently experiencing problems recruiting drivers, so there are a lot of new, non-local drivers around, which doesn't help. It's also relatively expensive.
The busway can be more reliable, at least where it is off-road, because there's no traffic, and there is at-stop ticketing on the busway. However, the route from the northern villages to the Science Park is a victim of its own success, and the buses can be full before they reach the closer villages e.g. Histon.
But also, if your son is used to London, the villages may just be too quiet for him. Cambridge itself isn't exactly a big city, but there will be more going on. If villages are okay, he could also consider Milton as just about within walking distance. Both Histon and Milton have decent off-road routes to the Science Park, so are also a good option for novice cycling. Outspoken Training, based in the area, offer training if he wants to build confidence cycling, as it really is the quickest way to get around the city.
The good news is that Chesterton / Kings Hedges / Arbury / Orchard Park are among the cheapest areas of the city, and any of them would be fine for distance to the Science Park. There's also a new train station, Cambridge North, which is useful for trips to London, once they get the national train mess sorted out.