Singapore city tour , harbour cruise , itinerary suggestions

Scenario:
4Days 3Nights in Singapore: I have a couple of friends coming to Singapore where they will be spending here in Singapore for four days. Since i’m working during the day, I will not have the time to show them some popular sightseeing.

What I ‘m thinking is to put them on tours during the day and taking them out for a drink after work myself. Some of the things I have in mind for them: an orientation tour of the city , night safari , harbour cruise, and sentosa musical fountain and cable car.
Can you suggest an itinerary for their first and second day in Singapore?A. Sign up your friends on the morning city tour on the first day they are here. The pick up is 9am in the morning and bring them back to hotel around 1 where they can have their lunch.

Suggestions:
They can have the afternoon free to window shopping or relax by the pool or go back to have a second look at the places they have been during the city tour since they know their bearing.

On the same day,book them on the night safari tour which leaves at 6.30pm and back at 11pm where you can have a late supper together. Many food court still open at that time of night.
The following day sign them up for a morning cruise at 10am.
The cruise is two and a half hours and they should be back at the hotel around 1pm where you can have lunch together with them.

Sentosa transfer will pick them up at 3.30 pm to go up to the mountain where they will go on the cable car across to sentosa island to see the musical fountain and the lights show. And they can have dinner on the sentosa island itself.

After sentosa, an option is to meet up with them at singapore river where you can go for a drink or two with them . The sentosa guide will drop them off at a hotel nearby the river where you can walk together to restaurants or bars nearby.

They are open till late morning.