This is a really individual thing and there is no right answer. I agree with your DH that it is important for the two of you to have some couples times before the baby arrives, but I personally would be unable to leave a toddler for that long. Perhaps you could compromise and go away for just one or two nights instead? Or go somewhere where his parents are nearby so that you can spend some time with your son and some time alone? The main thing is that you are comfortable with the plans, otherwise you won't enjoy it. GL hun.