My friend learned claw hammer on a open back banjo and it struck me as particularly lightweight. I would guess it was in the 2-3 lbs. range but I'm really not sure. I think his was a 4 string. They are definitely more heavy than a strumstick, uke, or canjo and probably close to a guitarlele.
Instrument weight is highly variable though and you'd have to take it on a case by case basis. I am a hobbyist Flamenco guitar luthier and flamenco guitars, although nearly identical to the dimensions of a classical guitar, are historically much lighter because of the type of wood used as well as the thickness of the various parts of the guitar. Peg style tuners are lighter than machine heads. The great Spanish luthier Antonio de Torres (died 1892) famously made a papier-mache guitar (back and sides) with a high quality soundboard to prove the relative unimportance of the side/back woods, but also how essential the soundboard was to the overall sound quality of a guitar. Here are some weights of historical flamenco/classical guitars (Urlik):
1912 Saturnino Rojas, blanca/pegs, 905 g.
1913 Manuel Ramirez, blanca/pegs, 1230 g.
1922 Domingo Esteso, blanca/machines, 1110 g.
1930 Santos Hernandez, blanca/pegs, 1200 g.
1923 Modesto Borreguero, blanca/pegs, 1090 g.
1929 Miguel Rodriguez, blanca/machines, 1165 g.
1948 Marcelo Barbero, blanca/pegs, 1185 g.
1958 Marcelino Lopez, blanca/machines, 1190 g.
1957 Arcangel Fernandez, blanca/pegs, 1190 g.
1962 Jose Ramirez, blanca/pegs, 1145 g
1961 Hernandez y Aguado, blanca/machines, 1300 g.
1967 Marcelo Barbero (hijo), blanca/pegs, 1310 g.
1971 Paulino Bernabe, blanca/pegs, 1235 g.
1975 Gerundino Fernandez, negra/machines, 1620 g.
1988 Manuel Reyes, blanca/pegs, 1360 g.
Probably a lot more info than you were looking for but it's a big interest of mine and thought that it might be interesting to some considering the weight factor. I still think bringing a canjo or something like that is a great idea.