Chobe NP is a logical choice, in particular, the northern riverfront area for dense concentrations of wildlife & large elephant herds & easy access to the park from Kasane town, about 8 minutes drive to the Sedudu entrance gate.
On our self drive & guided river cruise during the dry season there were dense herds of eles, zebras, buffaloes, wildebeest & antelopes including the puku, only seen in this area in Botswana. Birdlife is varied & interesting. All can be seen from the river or from the park's riverfront drive lookouts, however, congestion can be an issue at peak viewing times. We avoided very early morning thus fewer vehicles to contend so a good experience.
The river cruise is interesting. We did the afternoon cruise often called the sunset cruise. We had just a few passengers as we booked a small boat intentionally. You will pay park fees on top of cruise cost. Some local agencies are located along President Avenue in Kasane town, you can walk in and book or get your guest house or accommodator to organise one for you.
One trip we did a self drive day trip from Maun into Moremi, however, it was a long day with some corrugations and sand driving, bumpy rough in part, so 4 wd obviously. Depends upon your child's tolerance to that type of ride, as to whether it would be "OK".
If the water levels permit it, you can arrange for day or multi day boat trips i.e. kayak, mokoro, from Maun. Old Bridge Backpackers, Maun organises such including a day trip to Chief's Island which includes a walk on the island . It is a game rich area, we did a walking safari on that island from our delta lodge which was a great experience. You could check with OBB to make sure kids age 9 are allowed but I don’t see any mention of age limit.
https://maun-backpackers.com/okavango-boating-safaris/
We did a local sunset cruise from Maun for a few hours on the Boro/Thamakalane river, interesting to watch the local color and movement along the river banks. FWIW both towns offer reasonably priced self cater or catered accommodation and it is feasible to visit the parks without spending a motza.
Edited: 19 October 2021, 01:04