I have not fished the river in the park but have fished the Marina lake. Knowing the river it will probably be weedy and clear and personally I would expect you to struggle. The Nene just isn't the river it used to be. However I would think along the lines of maggot over groundbait for roach & skimmers, hemp for roach and chopped worm for anything with fins.
Marina lake does have a good head of large roach to be had on pole/waggler and good bream if you can cast far enough out into the lake.
I have convinced the family that pitching the tent right up by the river is a good idea
So Im hoping to have the same swim for 3 days. I will try baiting up as you suggested and target the roach and skimmers.