The Tokugawas were more concerned with fixing their internal affairs and legitimizing their initially shaky rule over Japan. The problem with the samurai class was that it was too active for the Tokugawas after the ruthless conquest of Nobunaga and the ambitious war of Hideyoshi. Ieyasu wanted peace and isolation. The destabilization caused by guns, the Ikko-Ikki, and the Japanese Christians, combined with the invasion of Korea, taught the Tokugawa clan precisely that going out into the world as they were - until recently war-torn and ravaged by division - was a bad idea, especially for maintaining their own power.
You want an expansionist shogunate, you change the family to one more amenable to such western ideas. Have someone like Oda Nobunaga at the helm, or possibly a cabal of Christian daimyos.
---
In any case, the Tokugawa shogunate has few options to actually expand. Hideyoshi's Korean adventure already shows the difficulty of taking the eastern route, let alone taking China. They could spend more on colonizing Ezo and the north before the Russians get it, but to what end?
And of course, there is Taiwan and the south, malaria-infested and full of sullen natives. A concerted effort with the Dutchmen to conquer it at the beginning of the Edo period could possibly be enough to take it, but again, to what end? Those islands were where all those exiled Japanese nobles went to escape religious persecution.
As for colonization, well, the closest OTL thing I can remember is the Kingdom of Ryukyu which was vassalized by the Shimazu. So, I guess it can work?