Yes I think you have a good chance to get some upgrade, but in general rooms (at least the ones I always had) are quite spacious anyhow. You will be right in the midst of the centre in a positive way and can easily walk everywhere and get to know the city and its people. Depending on time of year this will be quite different as spring/summer brings everyone out, lot's of terraces and restaurants to enjoy. In terms of what to do it really depends what your interests are, but I guess good to read up a bit on Bulgaria, history, and am sure you will figure out what you would like to see, there are several interesting places not to far, you got the mountains nearby etc. Good to find ways to get to know the country and its people a bit while there gven you will adopt a child. If you have a full day or more available you could venture a bit further, or even make day trip to Varna, on the Black Sea coast. Flights are $50-100 return and less than an hour. Again, for your second trip there will be lots to do, but nicer weather will probably make it easier as you can simply enjoy outside life. In any case enjoy and all the best for you and your family!