I too have a lovely girl, 5 year's old who growls and is deceptively aggressive towards ALL other dogs of non Basenji lineage. She does not like female B's and will only play with male's of her own club. The only luck I have had in getting her to accept play with other dogs is when the other dogs are considerably bigger than she is, then she will run and try a little bit to be dominant with them, but true to big dog's, they just mow her down….which is pretty funny I must say. Pipet has played well Great Dane's, Pitbulls (males) and German Shepard's. But Golden's, Lab's, Coliie's, any other similar of slightly larger dog is growled at....this happens mostly (in my mind) when they are all on leashes and slightly restrained, when she left in a big space where she can run away or get snarly and then run, she seems to cool out pretty fast, this is also true of much smaller dogs in a big yard (she will growl at them on the leash, but not so much in an open space).
I may be babbling, I don't know what to suggest but I do think that as they are so young, they have a lot to learn and are being a bit childish, Pip was like that as pup too, but at about 2 year's she began to really want to play. As long as the other dogs want to keep moving she is OK....and I never let her near food when around other animals, that doesn't work out. Trial and error....it may your path to just let the two Basenji's you have do all the running and playing just by themselves...which is no bad thing as there is far less chance of them catching other dogs ailments and or getting hurt in a fight. Pipet likes to be alone, she loves just being with me. I am hoping to adopt a male Basenji to keep her busy.....be happy you have Basenji's and that they get along....that may have to be enough. GOOD LUCK!