Smallish town near Prague

[Celeriacacaca]

I"m looking for a town/area not too far from Prague to go with teen DCs for several days to chill after a couple of days in Prague. Would like to be accessible to the countryside but still able to walk to restaurants, market etc. We're travelling by train. Also, any hotel recommendations please? Ideally with a pool.

It's not near Prague, but the best place in CZ I know of to relax is Luhačovice. It's a beautiful spa town in Moravia. I believe you can get there by train now, and it is in a wonderful verdant valley, with a lake nearby, and has a few pleasant restaurants etc..

Can't recommend any hotels in particular, but I suspect they won't be particularly expensive.

About 80 km north of Prague close to Česká Lípa is Máchovo jezero – Lake Mácha. You can stay on the lakeside, take one of the many walks, visit nearby castles such as Bezděz and Houska, breath fresh air and relax. You can also shop in nearby Nový Bor – one of the centres of the glass industry, visit its glass museum, and depending on the time of year, pick your own blueberries or mushrooms in the forest. There are two towns (well, villages) on the lake – Doksy and Staré Splavy. In Staré Splavy there are a number of pubs and restaurants, a sandy beach, a small port with boats for hire and (importantly for teenagers) an aquapark!
There are several hotels and guest houses. Vila Terezie has large family suites and guests get discounts at several partner restaurants in the local area. Hotel Port Doksy has a heated outdoor pool, an indoor pool and 2 bowling lanes, as well as tennis, mini golf and beach volleyball courts. Front desk offers possibilities for renting bikes, as well as rowboats and pedal boats for use at the lake. The train station is just 750 yards away.
I would recommend Pension Rut. It is right on the lake and has a shady wide terrace and garden. It is simple but clean, easy on the eye and very reasonably priced with nice homemade breakfast and friendly and welcoming owners..
You can get to Staré Splavy from Prague by train.

Thank you both - really helpful. I'll look at them now. Particularly like the sound of the land RiceK.