Sorry to be a party pooper but I'd hate to see you waste your money, so my opinion is this....
Kits are great BUT they are basically hand-built by amateurs. Some are good amateurs, others (like me) are hopeless beginners who just happened to have enough cash to fulfill their dreams. As such, most kits will break down regularly (just read some of the posts on this and other forums) . If you're happy working on them yourself, no problem but you can't usually just take them to a local garage and, anyway, that will cost too much. Also, they can be time-consuming and with your young kids, you'll be pushed to get time to go on runs, never mind fix it.
If you just want a fun car that you don't want to tinker with, just drive, you're probably better off with an MX5. I don't think kits depreciate any slower than normal cars.
Sorry to sound negative but you need to be honest with yourself about what you want to do with it and seriously think about if you have time. I specifically waited until my kids were over the age of 10 before I started my build and even then, I still have to fight with my wife to go out on weekends