Personally, i would get rid of the cars since your not going to enjoy racing with out your wife. Building an additional garage will be costly if you don't sell the two cars or maybe even sell the three cars. What I would do is get a mini van or a Suburban with three rows of seats since they have a nice trunk, because going on trips you'll need that extra space. What I would do when you child grows up to about 3yrs old, would to buy a Ti then swap the motor again and race it with your wife and have a baby sitter watch over your child while your racing. Maybe the market will be better in three years maybe not, that's might be the only thing from you getting your asking price.
If you buy a GT3 RS will it be fully track prepped when you buy it or will you do all that by your self? Or I would just not race at all
i know that racing will always be in your system its like a drug
, but since you and your wife are expecting I wouldn't race at all. Or what I was thinking when I read your post was keep one of the Ti's and sell the Z4 and the other Ti or the other way around and sell the Ti's and keep the Z4.
Such a difficult decision to make, but I would do whatever makes you happy, I hope this helps out.