Two stops with different purposes
Kwame Nkrumah Memorial Park focuses on Ghana's first president. Independence Square is a national ceremonial space and landmark. They can complement one another, but they shouldn't be treated as two versions of the same visit.
Choose the park if you want to give time to the person and history it interprets. Choose the square for a shorter landmark-focused outing, subject to current public access.
Budget attention as well as minutes
A museum visit needs time to read and listen. A landmark stop may involve more time outdoors than you expect. Put the more demanding visit first if your group tends to lose energy later in the day.
If both fit, allow a break between them. Don't reserve a meal so tightly that the museum becomes a hurried walk to the exit.
Check what is accessible that day
Public events and site arrangements can affect your visit. Confirm access instead of assuming a photograph shows the conditions you'll encounter. Ask separately about any viewpoint or building you hope to enter.
Compare Kwame Nkrumah Memorial Park with Independence Square, then decide which is essential. Keeping one optional is useful when you have only a short window in central Accra.