Hi Rosie,
It is a very busy trip. The optional tours were Moscow by night at €44 and a Russian Folk Show in Saint Peterburg at €66. I would book them, both to be recommended. The folk show was 45 mins then a break with champagne, vodka and hors d'oeuvres, then another 45 minutes, The show is inside one of the many old palaces in Saint Petersburg. The hotel in Moscow was a bit away from the centre and not in a really touristy area, although there was a metro station nearby (however, they are all signposted in Russian and no English so it doesn't make it easy to wander around much). One of our group did venture out to Gorky Park on his own and managed OK. There's not a lot of free time but you do a lot of walking and will probably find you want to have a break.
Both hotels were good standard and both had hairdryers, tea/coffee making facilities and mini bar fridges. Lots of bars and restaurants in both too.
I did take Euros and some roubles with me, but it was much easier to take the money out of the ATMs within the hotel, they will dispense roubles and Euros and instructions were in English. Just make sure you advise your bank you may be using your card in Russia.
The hotel in Saint Petersburg is a Holiday Inn on Moskovsky Prospeckt, I found this city much easier to navigate as it is laid out in a more European style (apparently plans were based on Amsterdam streets). Again you will be very busy but there is some free time, maybe a couple of hours one afternoon and the evenings other than the folk show. The area around this hotel is more a shopping area and again there's a metro station nearby, also the Moscow Gates and further along the road there is yet another church to visit!
Remember to take a headscarf as you will need it to cover your hair in the many active churches you will be visiting.
In some of the palaces you are not allowed to carry large handbags or day rucksacks, only a small bag is allowed. None of the active churches or the Kremlin Armoury allow photography. You could take photographs inside Peterhof, Peter & Paul Fortress, The Hermitage and Catherines' Palace at Pushkin.
I'm sure you'll have a great time!
Any other questions don't hesitate to ask.
Happy Holidays!
Jacqueline