Also in terms of solids, IIRC the recommendation is that by 12 months, about 25% of baby's intake should be solids -- which means that even at 12 months, the vast majority of baby's intake should be breastmilk. I think the best way to think of it is that before a year of age, foods are to explore textures and tastes and they're pretty much "extras," but breastmilk is the Main Food.
So, as a pp said - nurse before giving solids, and don't tank baby up on solids (since they are lower in nutrients and lower in calories than breastmilk, anyway). A lot of the conventional wisdom about what babies should be doing in re: eating in the USA, is based on the old paradigm of formula-fed infants (from back when the formulas didn't have vitamins or anything added and nutrition was really, really lacking in ff'd babies - so it was all about getting babies onto solids as quickly as they could, to save money and to get more nutrients into the baby).
Don't feel bad about the past. It sounds like you've researched and are learning more - so you can apply it now. And your 7 year old will see you confidently and comfortably nursing her baby brother past 9 months, and know that it's normal and possible.
My mom bf'd all 7 of us. I weaned at 10 months (nursing strike/Mom was 4 months pregnant) - everyone else nursed 'til 15ish months. Mom tanked us up on solids per the doctors' advice and introduced cow's milk at meal times at 8 months (again, per the doctors' advice). She didn't know any better, she did the best she could with what she knew back then (70's), and truly - she nursed far, far longer than most women of her generation.
. It's all a learning curve.