1. Pete and I are playing/play Scrabble at the moment. - playing (present continuous tense)
2. My sister meets/is meeting her friends every afternoon. - is meeting (present continuous tense)
3. He is not having/doesn't have a shower right now. - doesn't have (present simple tense)
4. I go/am going to see my grandparents every Saturday morning. - am going (present continuous tense for future plan)
5. George is learning/learns to windsurf these days. - is learning (present continuous tense)