Yes — half day covers both comfortably. Islamic Arts Museum (Jalan Lembah Perdana, near Perdana Botanical Gardens) needs 2–3 hours if you like architecture and textiles; entry around RM14. National Mosque (Masjid Negara) is 10 minutes walk away — free entry, robes provided for visitors, closed to tourists during Friday 12–3pm prayers. Morning visit: mosque first at 9am open, then museum when it opens 10am (check current hours). Dress modest (shoulders/knees covered). Combine with a Lake Gardens stroll if weather is clear. Grab from Bukit Bintang is RM12–18. Not as crowded as Petronas — underrated stop.
Museum cafe is decent lunch spot — air con break before the mosque walk.
Kids bored in museum after 90 min — mosque courtyard was the highlight for them.