First of all thank you to everyone with the thoughtful comments.
My $0.02
What's the Miata worth? Miata's are cute, but they are impractical (more like a toy). You've got SL's. There's no room for toys when you've got SL's.
Have a mechanic look at the Accord before doing anything. Your parents (possibly without knowing it) may be unloading a POS headache/money pit on you.
The Miata is worth $3,000-4,000.
I'll push back a little on the impractical comment. For 90% of my driving, I am the only person in the car, so having extra seats doesn't really increase the practicality. To me what makes a practical commuter car is, good gas mileage, cheap replacement parts, easy repairs, and comfortable quite ride. The Miata checks off 3 out of 4 of those. It also has the added benefit of having reached the bottom of it's depreciation curve and starting to increase in value which means it is hundreds of dollars per year cheaper to own than almost anything else.
It's actually surprisingly useful for transporting stuff too if the weather is decent. I've moved bikes, lumber, and a christmas tree in the passenger seat.
But point taken, the Miata probably makes the least sense for a family of five, and I appreciate everyone who has pointed that out.
From a practical standpoint, it seems like it would make the most sense to sell the Miata and have two cars that you're capable of transporting the kids in - for example, you might need to take one kid somewhere while your wife takes the other kid somewhere else. But I'm not emotionally attached to your Miata while it sounds like you are, so it's hard for me to know how much weight to give that factor.
In a situation where one kid needs to go one place and the other kid(s) need to go somewhere else, the Miata is fine because it has a passenger seat (with no airbag).
I calculated the break even point for options B and C using 6% interest for the time value of money (I suppose the marginal rate on your student loans would be a better calculation).
Option B: Sell for $2000, increase monthly expense by $43; break even in about 4.5 years.
Option C: Sell for $3000, increase monthly expense by $33; break even in more than 10 years.
The increase in monthly expenses for your free car seem to be pretty well offset by the value of the car you choose to replace. If you can get 4k for the Miata, you could be ahead for more than 15 years!
Thank you. This is a really helpful way for me to think about it.
If the problem is the Civic is cramped, I don't think an Accord fixes it. I've had both. You don't gain much space with an Accord. (I had a Civic coupe so much Accord did have more doors, which is good for kids.)
So in this case, I would not accept it
You are right that Accord isn't actually that much bigger than the Civic. However the two main issues that we have with the Civic is rear hip room, and trunk space. The Accord has 3.7" more rear hip width and a 40% larger trunk. This would go a long way in terms of making it more comfortable to fit three in the back seat and make it much easier to transport strollers and kid stuff.
And it sounds a bit like an obligation. How long do they have to keep it before it's "ok" to trade it, for instance? It sounds like OPs parents might hold a grudge if they got rid of it.
My parents are really laid back about stuff like that. Asking for money instead of the car or selling it immediately would probably push them too far. But, if we didn't feel like it wasn't working out and we wanted to sell it after a year, I don't think they would be mad.
My question would be - do you think selling the Miata would be a + or - for your wife on the path toward frugality? If she would see it as you choosing the family's financial health over your own personal pleasure of driving Miata sometimes, it could be a positive nudge in her path to embracing your frugality or maybe even joining you. When we bear the personal "cost" of frugality, it can inspire some spouses. I also think it's healthy in moving past emotional attachments to objects (it's ok to have loved your Miata and still not keep it indefinitely). On the other hand, if your wife would see it as you depriving yourself & use it to justify another spend (after all, you got the $ for the Miata!), then I can see this as not actually netting the expected benefit AND turning into a source of frustration (if you're not keeping the savings, how would you feel about giving up the Miata?).
I've brought up selling the Miata quite a few times in the last few years and she always says she would be too sad if I sold it. This is in spite of the fact that she hates driving it and hasn't ridden in the passenger seat since our 2 year old was born. I've driven the car since before we met and she sees it as an important part of my identity. FWIW, my 13 year old hates the idea of getting rid of the car even more.
As far as her seeing me choosing my family's financial health over my personal pleasure. She already thinks I do this too much.
If I sold it would she use it to justify another spend? Probably not. She does a pretty good job of sticking to the budget, she just isn't interested sacrificing her own personal pleasure to nearly the extent I am.
Sell civic and use accord.
Or sell civic and get the wagon/minivan.
I love my 2009 honda odyssey bought this year.
Being able to change kids diapers/clothes while almost standing up is a very important part of life right now.
Gas is kind of killing as it only gets 15 mpg but I can tell you it is worth it for me and especially my wife who does not break her back getting the baby with the car seat in and out.
15mpg Ouch! At our 11,000 miles per year that is an extra $124 in gas a month compared to our current car. I'll gladly take my kid to the nearest restroom to change a diaper for that kind of money.