You'll get better info if you give us a little better idea of your travel plans. Are you focusing on one area of the country, how often you plan to move, etc. We are retired and been full timing for one year in a 43' Toy Hauler in which we carry out Goldwing motorcycle. We put 11,000 miles on last year, so fuel is an expense. Because of our rig size, we can rarely stay at state or nat'l parks. We have used various RV parks and resorts and our monthly expense with electric/water/sewer has been between 450 - $1100 per month. You'll often pay more for pull-thru sites or the premium sites it may take to comfortably accommodate your rig and family. If you can stay somewhere long enough to get a monthly rate, you can save some money and we did that when we wintered in south Alabama and central Florida this past winter. If you are somewhere that'll require you to use your furnace you can expect propane expenses to run quite a bit - up to $100 or more a month. We rarely need it but don't want to be in cold climates.
I cannot imagine 7 folks in one rig, but that's up to ya'll. As already stated, a TH will probably work better, BUT they are heavier by design and will increase the vehicle type and operating expenses for it. Ours has just 1 bathroom? But they have 2 bathroom models and Grand Design are rated for full-time use. As far as safety, we have never had an issue but do not stay in rough areas either. For the most part the RV community is friendly and helpful to each other. Of course we don't have kiddos with us to worry about.
Keep in mind that there will be monthly and annual maintenance to do on the rig and most things are not real inexpensive. The more you can do yourself, the more you'll be able to save. If you're handy with tools that'll be a money saver for you. Hope this helps.