You'll also have to remember that the majority of people who ever died are children. As kids were the most vulnerable to death, due to disease and being weaker than adults, they'll be the majority.
So, in fact, it may not be that hard. If they're babies/toddlers, it will be rather easy to adapt them to today, as they never learnt that much. If they're older, try grouping them together with people from the same time period. Don't worry too much about age, as each age has its own benefits. Also, put a few adults from the same time period into each group, as the children can, surprisingly, help them adapt to the new time.
Although communication can be hard, language experts will be helpful in communication with Greeks, Romans or Gauls, and soon, there will be many different languages, spoken between groups of different time periods.
So, to summarise, adapt the younger children first, then separate into groups according to their time period. Then add older kids from the same time period into the mix. Also, try communications between adults-language experts are the key! Then, soon, add adults from the same time period in each of the groups, and get everyone to teach their bit in the group(Try grouping families together, so a group may be of about 4 families each.) Also, try introducing groups to other groups, so there can be less discrimination. Soon, new sorts of languages can be formed with one another, and you have new, vibrant communities getting along to the 21st century
(Also, a question- will the resurrected people die again?)