There's Apartotel Christina, same area, almost as nice. Otherwise as I mentioned I like the Palacio very much. You are going to be gone alot on your dental days so I know you want her and the baby to be in a nice place.
For me the beach is a little far for day tripping although not ridiculous if that's what you want to do. Jaco is the closest, 2 hours with the baby in the car? but the least rep of CR pacific
beaches. Playa Hermosa another 5 miles south is alot nicer beach wise. Check out this webcam on that beach and I know this is a pretty nice hotel, surfer themed, but OK.
http://surfinnhermosa.com/#livecamI spend as little time as I can in SJ. I am addicted to ManAnt. and my novia is near, but I have had the dental stuff and the medical stuff and so sometimes I have to be there. If you decide to go to the beach and spend a night or two, that would be my destination, 45 mins further S than Jaco but a magnif world class beach. I know Apart Christina will allow you to store a bunch of stuff there assuming you are going back to SJ and not direct to the airport. PM with your email if you have further q's and I'll be glad to help. This board has helped me many times and one must repay if one is knowledgeable, and I know that SJ to the beach thing as well as anybody, 15 years of multi yearly visits, but mainly Quepos/ManAnt.
To answer your q, I usually check out and head to Quepos and upon leaving drive directly to the airport. If that is your option, let me know and I'll direct you to my posts about doing that from the Autopista del Sol to the airport---you don't want to go all the way back to SJ, there's a much shorter way.
By the way, please post your dental experience when you get home, alot of guys are always interested.