If you have 7 days to spend in Stevenage, there are plenty of things you can do and places you can explore. Here are some suggestions:
Knebworth House is a beautiful country house and gardens with a rich history. It is definitely worth a visit if you are in the area. You can explore the house and the gardens, and learn about the history of the place. It should take you around 3-4 hours to explore everything properly.
If you are traveling with kids, the Adventure Island Playbarn is a great place to spend a day. It is an indoor soft play area with plenty of activities for children of all ages. You can relax whilst the children play, and grab a coffee or a snack at the on-site café. You can spend around 2-3 hours here.
Fairlands Valley Park has plenty of activities to offer, including a sailing lake, a water park, a café, and beautiful green open spaces. You can spend a whole day here, pack a picnic or grab some food from the café, and enjoy the views and the activities.
The St. Nicholas Church is a historic church in the heart of Stevenage, with beautiful architecture and a rich history. You can learn about the church's history and architecture, and explore the beautiful gardens. You can spend around an hour here.
As for places to stay, there are plenty of hotels and B&Bs in and around Stevenage. The Premier Inn Stevenage Central Hotel and the Novotel Stevenage Hotel are both great options, with comfortable rooms and great locations.