Commute + tow bike
 

I commute about 25 miles a day so I need something reasonably fast (able to sit comfortably at 18mph without a ridiculous amount of effort). I also need something that can be used to tow my son around woods/country parks etc. in his trailer at the weekends. I did have 2 bikes, a road bike and a hybrid which worked pretty well, but unfortunately some f***** stole them both from my garage last weekend. Could both of my bikes be replaced with a gravel bike or should I stick to my 2 bike formula? How rough can you go with these gravel bikes before you need a hybrid? I haven't ruled out an electric bike but my only issue with them is they're restricted to 15mph (in the UK at least). This is a bit useless for my flat commute, so I'm not sure how much assistance it will actually offer, but it would be a bit more rugged for the weekends I guess? Any advice would be gratefully received before I make an expensive mistake. Thanks.