introducing dogs on terratory

I am moving from the UK to Canada in a couple of months with my
Canadian wife and our 3 year-old labrador / staff / allsorts female -
Roxy. For a few weeks at least we will be staying with my mother-in-law
who has two Canadian Inuits - one male (5-7 years old) - Boomer, and
one female (11-12 years old) - Matissa. We are concerned about how to
introduce the two females to minimise the chance of a serious fight.

Matissa is alpha in the household and a fairly grumpy old thing. She is
not a particuarly active animal, but on a previous occasion has taken a
chunk out of another dog's ear when he was on her territory. After this
scuffle, the dispute appeared to pass and she allowed the visiting dog
to remain on the territory once she had asserted her dominance. Boomer
is a good-natured animal who is not particularly active most of the
time due to a hormone defficiency.

Roxy is a very active playful dog about the size of a small labrador,
who loves to play with bigger dogs, and will submit to them, although
she may wind them up to play with her. She can be distracted from
almost any dog by waving/throwing a stick.

We will be arriving with Roxy from the airport, and she will
undoubtedly be distressed having been locked up in a crate for 9 or 10
hours. My mother-in-law's home has quite a large house and garden with
outdoor kennels for the dogs, although they are allowed indoors on the
ground floor and sleep inside too. The back garden is fenced off to
keep the dogs in, and the front garden & driveway are not.

The most common suggestion in this situation seems to be that the
animals should be introduced off the territory. Unfortunately I cannot
see how under the circumstances we could do this. We may be able to
take the animals off the grounds to an adjacent field for a walk, but
only on their leads. Roxy often growls at other dogs when she is on her
lead, and certainly would not feel comfortable letting her off the lead
in a strange new place which is not fenced in. It will be dark when we
arrive and there are busy roads in the area.

The tools we have at our disposal are the house, a large fenced-in
garden containing two tethers with long ropes, and a long driveway with
large grassy verges (not fenced). What would be the best possible
solution to introduce these dogs, in particular the two females, within
these restrictions?