Be assured that your little person can be mobile! You can make oxygen "wet" by adding a bubbler humidifier. A 'bubbler' humidifier is either pre-filled or refillable with sterile or filtered water (never tap water). You can get a portable oxygen concentrator device that can have a bubbler humidifier attached to it. There are several battery operated portable oxygen concentrators on the market that will allow humidifiers to be attached so that your little person can have "wet" oxygen" and does not have to be bed bound.
Note that most portable oxygen concentrators only give 3 liters per minute continuous flow. All of them go up to 5 or 6 liters per minute "pulse dose flow" The brand I recommend is Devilbiss iGo portable oxygen concentrator since it does have continuous flow of 3 liters per minute and has the longest battery life of the continuous flow units. It also has a bubbler humidifier kit available specifically for this unit.
See the Devilbliss iGo oxygen concentrator link below.