My first question, if it's not too nosy is .... what age group? What appeals to kids (mid 20's and down) might well not be what appeals to mid-40's and up. Rolling skating may well be a problem if she's got a zimmer frame. So pick accordingly.
Second, I'd suggest a plan involving two options, one for fair weather and one in case the British weather does what it's famous for.
Perhaps depending on age group, pick a nice location close to a nice park. Then, find a coffee shop and a nice pub in easy walking distance, or better yet (if possible) in the park. Then suggest "coffee shop .... unless you'd prefer a pub?" You can then
suggest a walk in the park, and see if she's happy with that. It keeps the option open.
I'd also phrase it in such a way as to be a suggestion, leaving the option open for her to suggest something which she may either prefer or feel more comfortable with. For a first meeting, she may prefer something with more people around, like a coffee shop in a shopping centre. A park, however picturesque, may be perceived as a bit .... risky.
So the above "coffee shop .... unless you'd prefer a pub?" Might become "Do you fancy a "coffee shop or a pub, perhaps by the park .... unless you'd prefer something more town centre?"
It's also somewhat variable according to exact timing. If she suggests 12:00, I's take it as a hint at lunch. If she suggest 3PM, I'd take it as a hint at no lunch.
Or, if a car is involved, I'd consider something a little more ... interesting. Close to me, there's a really nice farm shop with a very nice cafe/restaurant. It's very good quality food, extremely fresh, and most of it directly from that or neighbouring farms. It's out on the country, so for a first date I'd only suggest it on a "meet you there" basis, as she may not want to get in a car with a stranger and go driving out in the countryside, but once there, you've got staff around and there's usually other customers.
And, as that place has a few attractions for kids (go see the cute little chicks in their brooding pens, or the lamb/pig section, etc) it's also a good possibility for a return trip, later on (if all works out) with the kids in tow.
All told, I'd say it's a good idea to have a few options planned so you can be versatile, but then you have to somewhat play it by ear, and pick up any signals she sends as to what's a good idea and what's not, especially given that it's a first date through an agency and she has
no idea what or who to expect.
Oh, and .... good luck.