With a less than aviation mad woman (which is 99% of them) you have to pick your day for a trip carefully. My wonderful girlfriend of 7.4 years is very happy to fly with me, and we have been to lots of places, as far as Crete or S. Spain, but I have to pick the wx carefully. Personally I don't do heavy IMC enroute anyway (icing conditions are never predictable, who wants to be in a tumble dryer, etc) but with her I have to be more careful still.
Loads of male pilots have given up flying permanently due to pressure from their women, and it always seems so pointless, because a relationship should be one of mutual support for each other's "projects".
Short trips (1-day or overnight) offer the best value because you can visit some nice city, and high pressure weather is often present for a few days at a time which is just right.
At the other end of the scale, if going away for say 2 weeks, it is no use trying to predict the return weather so you just go, keeing the dates a bit flexible and sometimes she will take a commercial flight back. It's no big deal, and on the few occassions we did that, I nearly always had a perfect flight back. Only once I had to divert due to wx (to Lydd, ILS, overnight in a hotel).
When we do a long trip, we set aside 2-3 days for getting out of the UK, and about 75% of the time we manage to get away on the first day (one always flies on the first technically suitable day, even if the following day "looks perfect"). On another 20% of the time we get away on day 2 or day 3. Only once did we have to cancel the flying holiday and take an airline somewhere, but we did a flying holiday later in the year anyway.
Avoid stops in places where you are not stopping for a reason i.e. pick any fuel stops to be overnight stay places anyway, so if you have to stay an extra night it doesn't matter.
With an IR it is easier but not as much easier as most PPLs would think - the weather doesn't care for what papers you've got. What an IR does, at least 90% of the time, is allow you to access airspace which the bl00dy ATC units in question should have let you into under VFR if only they complied with ICAO airspace classification and were not so ana11y retarded. On most long IFR trips (and I always fly IFR when going abroad, nowadays) I log very little actual instrument time; often 15 mins in 15hrs of flying.