27x1-1/4" wide tires will fit and, in my opinion, are a better tire size for general riding. Just a wee bit fatter tire allows more comfort and control over rough roads or surfaces.
27x1-1/4" is very close in size to (but not compatible with) 700x32c, which is a perfect size for any non-competition road riding.
In the future, if you wish to modernize the bikes, the wheels can likely be replaced with 700C size wheels, which is the modern standard. There is no inherent advantage to one wheel size over another, just with 700C you have a much wider selection of tires and rims available, while 27" wheels are basically obsolete and have only a few tire choices available.