Don't go crazy with a new truck. Find something you can tow safely with what you have and work our way up to your dream camper. Most small kids could care less about the accomodations and will be so worn out by the end of the first night you could stand them up in the closet. We had 4 kids (1, 3, 8, 10) and started in a Coleman Pop-up. Moved to our first hard sided trailer (also a Coleman) after a weekend of hard rain pulled by a GMC Safari. The salesman also said "Oh yeah, that'll pull it fine". What a load of BS. After a white knuckle trip to Disney World I bought the Excursion. Several trailers later we now have our dream rig,
Take your time, do your homework and enjoy the experince. If your going to enjoy the lifestyle, accept the fact that your needs will change and you may have to go through several trailers/Tow vehicles to get to the sweat spot. Just remember to give your self some cushion.