A few places that either have playrooms for kids, a nanny and/or special children's events during the weekend. Check their reviews on russia.inyourpocket.com and their websites for more info.
Миллионная ул., 4/1 (Аптекарский пер.), San Petersburgo, San Petersburgo
Restaurante francés · Исторический центр · 106 tips y reseñas
In Your Pocket: Close to the Hermitage & Saviour on the Spilt Blood. Cooking classes for kids http://www.inyourpocket.com/russia/st-petersburg/Restaurants-in-St-Petersburg/finedining/Legran_113728v
Невский просп., 43 (ул. Рубинштейна), San Petersburgo, San Petersburgo
Restaurante italiano · Владимирский округ · 1023 tips y reseñas
In Your Pocket: Chain of Italian restaurants with playrooms for kids http://www.inyourpocket.com/russia/st-petersburg/Restaurants-in-St-Petersburg/italian/Marcellis_60152v
пр. Добролюбова, 16, San Petersburgo, San Petersburgo
Restaurante de Europa del Este · Округ Введенский · 39 tips y reseñas
In Your Pocket: Fresh Caucasian food in a nice & bright environment near Sportivnaya metro, with playroom http://www.inyourpocket.com/russia/st-petersburg/Restaurants-in-St-Petersburg/caucasian/Djigiteria_114133v
Конногвардейский бул., 4 (Почтамтский пер.), San Petersburgo, San Petersburgo
Steakhouse · Адмиралтейский округ · 325 tips y reseñas
In Your Pocket: The name says it all, great steaks. Playroom for kids, close to Isaac's Cathedral http://www.inyourpocket.com/russia/st-petersburg/Restaurants-in-St-Petersburg/steak/Stroganoff-Steakhouse_36431v