I think Roger will confirm, but an 8.2 is a LARGE sail for someone at your skill level and weight. Something around a 6 meter will be best for you to learn, but you could probably manage with a 6.5 or 7.0, but it will be a little more challenging.
Most adult beginners start with a 5.0 to 6.0 sail and after they become pretty proficient at tacking, light wind gybing, daggerboard use, plus upwind & downwind work, they will want to move into planing (including harness use & footstraps) and more speed. This either takes 20+ knots of wind (not a good idea) or a larger sail. A 7.5 is in the range of a second sail. A third sail may depend on where you live and the typical conditions, plus - your family needs. Since you have 7 year old, a 5.0 will be BIG to learn on, so there are a lot of options as you build your quiver. A 4.0 for your 7 year old or an 8.5 for you and 12 knot winds to plane?
Now it's Roger's turn to offer a few suggestions.
Formula 160; iSonic 111; HiFly Move 105; Tiga 263; '85 Mistral Superlight.
Maui Sails TR 11.0; 9.2; 8.4; 7.6; 6.6; Maui Sails Switch 6.0; 5.2; Maui Sails Global 4.5; 4.0.