Although it is less that 100km from Lisbon, I frequently use the Ibis Setubal Hotel which is about 40km from Lisbon Aiport on the old Lisbon to Algarve road.
See: http://www.accorhotels.com/gb/hotel-1275-ibis-setubal/index.shtml
It is ideal for kids as there is a garden and a pool.
Access is via Setubal and you can rejoin the motorway at Marateca.
See: http://www.accorhotels.com/gb/hotel-1275-ibis-setubal/location.shtml
Further south there are not many hotels of quality as folk tend to make the Lisbon to Algarve run in one fell swoop.
In my opinion and experience this would be the best option.
You are then less than 2 hours by motorway from Guia in the morning.
Be aware that the motorway is a toll road.
