This is likely a good idea. My only reservation would be that you might have to pay tax on the $700 gain (although it might be less if some of that is from dividends, which you've already paid tax on), and you might might not have to pay tax on the gains if you sell in retirement. Are you currently above the 0% long term capital gains tax bracket? Will you be below it in retirement.
It sounds like you have enough cash to make the contribution, but want to keep it in cash for the moment due to new baby? You might consider
https://www.bogleheads.org/wiki/Roth_IRA_as_an_emergency_fund. If you contribute to Roth, but keep the contribution in a money market fund you can either withdraw from the Roth (contributions can be withdrawn tax and penalty free) or decide to sell from taxable if/when you have the emergency. Chances are you won't have an emergency and you'll end up with money in Roth you can invest and won't have had to sell taxable.
Last question: is this your 2019 contribution or your 2020 contribution you're considering? If it's the 2020 contribution, then you have until April 15, 2021, so there isn't any hurry and you might just consider holding off and not worrying about it right now. Maybe not totally optimal, but not a big deal.