You are blessed to have been able to take the time you have taken thus far. I went back to work as a full time psychologist and part-time grad student when my son was 13 weeks old. It broke my heart, but he was fine with it, honestly. He loves "baby school" and has a little group of friends.
It does not sound like you are financially able to stay home and still have all of the things that you "want"- like the cars and a bigger house. Something will need to "give". Step back and think about your long-term finances. You have at least two sets of braces, activities, tuitions, etc to consider. It sounds like your husband may have an increased income at some point, but right now you both should be contributing.
There are other options aside from returning to a school system- you could tutor privately or work for a learning center. You could also register with the local schools to be a sub. It's per diem, but you could choose when you work. If you are going back part-time benefits are not a factor, but consider the retirement contributions.
If you decide to stay home, don't regret the things you have to give-up. Consider trading-in your cars for smaller, previously owned cars. Live with the small house and put away the extra money for a down-payment much later on.
As much as I hate to admit it, we can't have it all and as mothers and professionals we need to be okay with this. I went through this about six months ago while finishing my graduate program. My husband and I sat down and talked about where we want to be as a family in 5yrs, 10 yrs and beyond. For us, having me work full time and investing in my education was a good choice. It will provide us with a more secure future and will allow our children (we definitely want more) to attend a private school if we choose and to attend college without worrying about loans.
We make every minute count with my son and have long-since stopped feeling guilty for having him at baby school. He's learning social skills that he would not learn from spending all of his time with me. He's happy, loved and healthy and really that's all that matters. The laundry and cleaning get done when we have a few minutes, but bedtime stories are essential. It's about priorities and choices- short and long term.
Best wishes.