How do you manage the summer heat if there is no time to get out of the city? Any suggestions on how to cool down in Manila?

There are staycation areas within the city. You might want to consider that. But medyo pricey nga sya if you'll do it on a regular basis during the summer season. Mas tipid pa din kahit na mghapon nakabukas air con sa bahay. And store lots of fluids at home to keep the family hydrated.