Go see the bonobos by Lac de ma Vallée, Chutes de Zongo in Bas Congo and Bombo Lumene on the road to Kikwit. A BBQ on a sandbank on the Congo River is definitely also a must. Renting a boat for a day with a driver and all the gear tables, chairs, a suntent and a BBQ will cost around 150$ at the Yacht Club Kinshasa. The boat can take 8 people, so if you share the cost it is quite affordable. A truly unforgettable experience.
Don't forget to get some arts in Le marché des valeurs, sometimes called marché des voleurs... the first calling means market of value, the second in changing only one letter means market of thieves. Be prepared to haggle and don't pay the initial asking price that will be at least 60-75% over the final price if not more. For some more upscale art you can go to the Academie des Beaux Arts on Avenue Pierre Mulele formerly Avenue 24 Novembre or to Symphonie des Arts: towards Kintambo on the Boulevard du 30 Juin, turn right after the elephant when you see the barrier on your right... then it's on your left hand accross from the big colonial villa. A more time consuming but far more interesting and personal way to get to know the artists of the country would be to visit their private studios. Prices are high even there for paintings of Lema Kusa, Henri Kalama or Nshole, but worth every penny considering the quality of their works and their international career.
A more relax and fun way to buy street art is to have a beer at Surcouf: it's on the street off the boulevard 30 Juin towards Justice off the INSS building. Sit at a table and have a drink Primus is recommended and the artists will come and show all kinds of artworks all the time. The same rule on negotiating applies as at Marché des valeurs.
kinkole
Kinkole is a small village in the eastern part of the city's rural area. It's on the RN1 Boulevard Lumumba, further than the airport. It has a nice restaurant area where you can enjoy all the local food on a terrace. A lot of people come here to relax so there's a lot of people trying to get you into their business. If you go closer to the river there's a fisherman market where food from the river is brought. Be careful if you want to take pictures, you'll probably have to pay someone first as this is considered the international border.
jardin d'eden
Jardin d'Eden is a restaurant and music bar by the shores of the Nsele river, in the eastern part of the city's rural area. It is further than Kinkole, after the airport. There is a really relaxing athmosphere there. You can eat, listen to the live band playing Congolese classiscs or even take a boat on the river Nsele. The food and drinks are affordable for middle class.