Brussels is a highly connected city by air, bus and train. Flights, cars and tours can be booked online at www.lonelyplanet.com/bookings.
The best price found from United States to Brussels is on March 12th, 2019, travelling with Southwest Airlines. See more options, compare prices and book: search flights.
Travelling with kids in Brussels is rarely a problem, even at top-end establishments, but you will seldom see Belgian children running amok, and you will be expected to make sure that yours aren't either.
There are plenty of local projects in Brussels aimed at migrants and the homeless. If you'd like to help out, ask at the Use-It office for some guidance.