I was going to mention parkrun. It can, of course, depend on the terrain, but they actively encourage people with buggies to join in. It's a little annoying, naturally, when some speed merchant goes past you with one of these contraptions (and I'm a sub-20 minute runner, so not a total slouch), but it takes all sorts.
Double-plus good for what Muttley says. You're entering a bit of unknown here, but what it will do is give you a good idea of what you can cope with - and you'll have a PB you can beat next time. Good luck.