Have a house and land payment every month. We'll be here for the next 20 years at least God willing. Love it where I'm at, and we planned on what we wanted for now and the future, and our place fits the bill.
The question is, if you move, do you sell first or buy first? Have you had your house appraised and do you know what you'd qualify for on a loan?
The fist time I went to the doctor in a long time was when I thought I was showing signs of having a heart attack. Turns out it was stress knowing that I was going to have two house payments when we bought our current place 6 years ago and we still had the house payment where we were living in at the time. Luckily, we sold that house in less than 3 months, but today's housing market isn't like back then. If you decide to move, I'd look at selling your house first with the condition you have three months to get out, then you're house shopping QUICK. Beats the alternative of having two payments and the stress that can come with it. Thing is to line all of the paperwork up and what what you can and can't do BEFOREHAND.
Ultimately if the house is too small for the family, I'm guessing sooner or later you're going to move. My buddy up north seems to be in the same situation as you. He just did some work on the house, increased it's value substantially, and they'll be putting it up on the market next year, and after it sells, try to find another place for his growing family.