I know you said you don't have T-Mobile, but if your phones are unlocked, you might prefer to avoid some SIM-hunting hassle and sign up for the T-Mobile Simple choice plan for just one month (no contract, cancel when trip is done, but hard credit check). $50 per phone and you have data in all 4 countries, plus free texting (and if absolutely necessary, paying 20 cents/min to make phone calls.

That's what I'm doing for my upcoming Europe trip. Last time in Europe, I bought a SIM card in each of 3 countries and spent about $70 total on the cheapest pay-as-you-go plan with data. I rarely want to make phone calls, and I only did so because I already paid for it.