I have been to St Petersburg with teens. They weren’t vegetarian though. This was in 2007 and we got our own Visas, I booked the flights and booked the hotel. I organised all the sightseeing and it was bloody hard work but absolutely wonderful at the same time. We never felt threatened but some older people won’t be helpful but young people are. Russians have a thing about taking a big deposit for Head sets in museums. They seem to think you will steal them! Shopping isn’t really worthwhile but Gum Department Store in Red Square is a gem and has good coffee! Get a clear idea of what you want to see before you go and take warm clothes. If you do a canal trip in St P it will be cold!
All the places to visit in St P have been mentioned but a real highlight is the Shuvalov Palace with the Faberge Museum which opened about 2 years ago. Just brilliant. The tombs of the Tzars are also worth a visit as is the whole Fortress of Peter and Paul.
Fast forward 7 years and DH and I went to Moscow and then to St Petersburg by high speed train. This time we went with Cox and Kings. We didn’t like the guide in a Moscow and the time was wasted by seeing things we were not interested in and not enough time to see what we did want to see. It had the advantage of staying at the Ritz Carlton with an amazing view of The Kremlin from the roof terrace. The whiz around the Kremlin museums was too short and we had to rush into the “Crown Jewels” ourselves, in the treasury, because the guide excluded it. Total madness. He also was surly when people didn’t want his show tickets at £75 pp. He did however do a great tour of the underground and it’s a must see. Anyone who thinks Moscow isn’t worth visiting is very wrong. Sergiev Possad was outstanding.
Finding restaurants was easy and there are Italian ones which can do vegetarian meals. As pp has said, The Lonely Planet guide will help greatly with restaurant choices and there are now some excellent ones in St P. Vietnamese, Italian and definitely not all Russian! If you can get tickets to the Bolshoi, get them. In St Petersburg go to the Marinsky if you can. These are two great ballet companies of the world.
St P had changed a lot. It’s much cleaner then before. Much more welcoming. There were lots of new restaurants and better hotels are opening all the time. Try and stay near Nevsky Prospect. You can walk to quite a few places but a tour will take you to the palaces outside St P. The fountains at the Peterhof may not be flowing in October, but they are truly amazing. Our guide was late and we didn’t get enough time there.
Personally I would pay for a Visa service as we did the second time. I would go to a decent hotel (we did) and I would go with a good quality tour company. Russian guides are more about doing what they want. The guide in Moscow announced we wouldn’t like the Tretyakov Gallery so we didn’t go. I was livid. Cox and Kings didn’t care either so don’t go with them. Our St P guide didn’t even stay with us until the end of the tour to Tsarko Selo. She was dropped off at home on the way back. They seem to do as little as possible.
However you could do a lot of exploring yourself but going to Tsarko Selo is not so easy if you are not on a tour. The Hermitage is easy and so is the Church of the Spilled Blood and the Faberge Museum. In 2007 the taxis were dire. I used the hotels cars. That would be very expensive now and taxis have improved. Both these cities are great and you are visiting somewhere that does feel different. The Russians can be welcoming but the old babushkas still exist! Russians have had it tough. You only have to hear about the siege of St P (Leningrad) to know that and they will tell you where the German troops got to when you go by the area. It is very close to the city. Younger people in restaurants tend to speak English now and many more people in museums.