need Yes that's a tricky route. It depends on what you like and don't like in transport.
If you like buses then you could probably just get one from Impington to the centre of cambridge, but it's likely to take a long time, with much stop-start traffic, unless you leave quite early, like 7am.
The other option maybe is to drive but also leave early in the morning (again like 7am) and just drive straight down the Histon Road into the city centre and park at one of the big multi-storey car parks. A whole day costs about £25.
The list of car parks is here:
en.parkopedia.co.uk/parking/carpark/park_street/cb5/cambridge/?arriving=201711031830&leaving=201711032030
A lot of people take a chance and try to park free on residential streets. You may get lucky if you just drive around a little bit north of the Victoria Road area. Tbh, though, if it was me and I was on a special trip like this, I'd probably just head straight for Park Street car park and pay for the day. The you can enjoy yourself.
I'm not totally sure when the traffic gets difficult. I used to drive at 9.30 and the inbound roads were still log-jammed at that point. I'm not sure how early you need to go to avoid it though. Maybe the people where you're staying would know?
Another fun idea is to drive to the outskirts of the city and walk in. I know you like a good stretch of the legs and Cambridge is a tiny city really. If you drove to Coton you could then easily walk to town. That would be a lovely walk too. I can't post links here, but google maps will show you the walking route. It's listed as a 45 minute walk, but I have an idea that you would quite enjoy that. It's proper lovely countryside there.
Sorry that it's complicated. Cambridge is kind of Boom-Town economically at the moment, which is why we're here, but the transport systems are still constrained by the medieval structure of the city and things are really difficult for people getting into the city.
I hope you have a good day.