You're going to love Merrimack. We just moved from there (unfortunately needed to go south for health reasons), but lived there 30+years and really liked it. Lobster Boat is great for seafood (and other stuff, if someone in the family doesn't like seafood); Silver Maple is good, great service - I felt like a princess - the wait staff was wonderful. Weathervane on 101 in Bedford is good also. Rt. 101A - quite a length of it - has many good restaurants. Someone mentioned Silos in Merrimack - it's very, very good.
Portsmouth has a fun childrens museum. Go there when you can. Charmingfare Farm in
Candia, I believe, is also fun. Check on their holiday festivities before you go. Kids will like it. The Clydesdale horses are housed in Merrimack and once a month, I think it's the first Sunday of the month, if they are not on tour, you go to the Annheuser plant (stables and gift shop on the grounds) and can pet the horses and have your picture taken with them. Kids love that.
King Kone, the ice cream stand in the heart of town, is a favorite in the summer. You know summer has arrived when King Kone opens. Great ice cream. Get a baby cone for yourself also. You'll be surprised at how big it is!!
There are concerts in the summer time - lots of other things going on in good weather.
Kids Cove is great for the younger set that likes to climb through tunnels, tires and fort-like structures. The town has the Merrimack Youth Association (MYA, as it's referred to), that has great sports programs. There is a wonderful library in town. I believe at Mastricola they flood a ground area for ice skating and hockey (at least they used to - check with the town). There is a lovely hiking trail called Heritage Trail that volunteers created a few years back. Great for spring, summer and fall hikes to the waterfall. Easy walk for the young and adults as well.
I'm sure there will be other suggestions - that's what comes to mind at the moment.
Enjoy. You've picked a great town to live in.