The OP asked about cruising with children. Silversea is lovely but there is absolutely nothing geared towards children, with a possible exception for some Alaska itineraries...or am I confusing that with Oceania? We have sailed on both but don't have children. In fact, some friends joked that we'd feel like kids on Silversea being among the youngest on board (in our 40s), but we're good with that.

OP - we have some frequent-cruiser friends with a young child who also enjoy higher-end travel, in general. They would echo the advice to consider Holland America whose ships are 1/2 the size of the NCL ships recommended previously, if crowds/lines are a concern (though you will still find both w HAL). On our one cruise w them the range of dress we saw on "formal" night was all over the place. HAL also offers "As You Wish" dining if you don't want a set time/table/group. We happened to know some others on our HAL cruise so we had a mix of dining with them and on our own at a table for 2 at whatever time and in whatever venue we preferred. They seem to offer a good number of Canada/New England itineraries in the summer if you want to start close to home for your first cruising experience.

Enjoy your trip!