I'm sorry that I don't know the sites around Cambridge but I'd suggest that as newbies you might want to pick a site for perhaps a weekend away not too far from home.
You are almost certain to forget something although a list might help and you might prefer to be fairly local and not too far from a caravan dealer / workshop / accessory shop for your first outing.
There are some lovely places around Northampton, are you a member of either the
Camping & Caravanning Club or the
Caravan Club?
Both clubs have, in addition to their main sites, quieter certified sites or certified locations, nominally restricted to 5 units which means that they are usually peaceful countryside retreats.
One C&CC certified site not far from your area that I can thoroughly recommend is
Woodlands Park certified site, a small well run site with ehu (electric hook up), run by Mrs Sue Calver. the site has a small but spotlessly clean toilet and shower portacabin type block and a reasonably quiet location.
Woodlands Park is very easy to get to, situated in the village of Clapham, just three miles north of the city of Bedford.
Clapham has welcoming pubs, takeaways, a few shops and a bus service from near to the campsite entrance into Bedford if you want a rest from driving.
The nearby Glenn Miller museum is open in April and there are other places of interest not far away.
Woodlands Park is open to C&CC members only and if you are not already a member you can join when you get on site.
We stay there for a few days every August, the site fee varies from £15-£19 per night depending on the season.