If getting around in an afternoon shower matters most, start with Eastin Grand Hotel Phayathai, 0.03 km from Phaya Thai BTS. The Airport Rail Link station is only 0.16 km away, which also simplifies luggage on arrival and departure days.
To shuttle between stations and malls around Phrom Phong, compare Emporium Suites by Chatrium (BTS 0.11 km), Hyatt Place Sukhumvit 24 (0.33 km) and Marriott Marquis Queen's Park (0.47 km). They differ by full kitchens, compact rooms and sheer room count.
For a central Sukhumvit stay with children, Sofitel Bangkok Sukhumvit and Holiday Inn Bangkok Sukhumvit are the candidates. Both register a kids' pool and a babysitting service, and Holiday Inn adds a playground.
With three generations travelling, Somerset Rama 9 offers a complimentary kids' club and kitchens, while Chatrium Sathon is compact with its own complimentary kids' club. Sathon sits far from stations, so check the shuttle service.