Howdee & Welcome to the forum
25C is fine for most tropical fish.
If the air bubbles are very fine (1mm) the filter could be leaking and sucking in air. If the bubbles are normal sized (about 2mm diameter) then it is probably just the filter outlet splashing on the surface and creating them. You should be able to reduce the amount of air bubbles by having the filter outlet just under the surface. Aim the outlet towards the surface and it will create surface turbulence but should minimise the bubbles.
A lot of people do a fishless cycle and allow the beneficial filter bacteria to build up over a month or so before they add fish. However, you can have fish in the tank while the filters develop the good bacteria. This is known as a fish in cycle. Basically you add a few fish to the tank several days after the tank has been filled up. You feed these fish once every couple of days and monitor the water quality for ammonia, nitrite & PH. You will need test kits for this purpose. Try to buy liquid test kits rather than paper strip kits. Some shops will do free water testing for you but it is often easier to do it yourself rather than zipping down to the shop every couple of days. Keep the test kits away from children as they contain toxic chemicals.
If the ammonia or nitrite levels get above 1ppm you do a partial 30-50% water change on the tank to dilute these levels. (Make sure any new water going into the tank is free of chlorine and has a similar temperature to the tank).
After a couple of weeks the ammonia levels should have gone up a bit and then come down. A few weeks later and the nitrite levels will have gone up and come down. Once both of these are on 0ppm and have been there for a couple of weeks, you can add some more fish. It generally takes about a month for the tank to cycle with fish in.
Some good fish to start with are zebra or leopard Danios, rosy, ruby, cherry or golden barbs. These are all schooling fish that need to be kept in groups of 6 or more. Therefore buy a group of 6 of one of these types of fish and use them to get the filters going. That way your little one can see the fish and you shouldn't have too many problems with water quality.
Once the tank has finished cycling you can add some more.
The other option is to get some plastic fish and have them floating around the tank while it cycles.