You do not need a visa, transit or otherwise and the Aeroflot agents in IAD know this [only SU on this route]. When you deplane in SVO, just follow the transit signs, go to the transit desk and they will sort you out by at least getting you through security and into the terminal where you can then get your boarding pass from another transit desk. I transit a few times a year in SVO and have not had a visa since around 2007.

That said, 7 hours with the family is a lot. I tend to stay no more than 4 hours. Duty free shopping is fine, but check the date on anything to eat or drink. It is often years past its date. The lounges are constantly fighting with other SkyTeam members, so they may not let you in or they may hold you to the 4-hour rule. Can be a little hit or miss. If you want to get the family in on one card, forget it now.