16 man should be a great size for what you want it for. Only two cautions I can think of. That footprint size can be challenging to find a spot to set it up (although you can always choke it down smaller), and are you sure you want 5 guys sleeping together?
Its a bit of a challenge to find good spots for my 8 man at times - and I think the 16 man is what, maybe 23ft diameter? The 5 guys thing is just some folks sleep lighter than others, some snore, and between five guys someone is likely getting up to pee every other hour throughout the night. We keep the stove going while relaxing and enjoying meals or drinks inside the tipi in the evening - but are not attempting to keep it heated throughout the night, so our plan is when we have more than say 3 in the eight man, we throw in another smaller shelter for some folks to sleep in. Everyone hangs out in the heated 8 man, set their gear out to breath and dry out, has a cocktail etc., but often a guy or 2 move to the extra shelter to sleep. As I get older I sleep lighter and some of my companions as they get older snore louder - just saying!
So a 16 would be great, but an 8 or 12 with a regular tent on the side would work great as well. Of course with horses you can bring the 16 and a nice 2 or 3 man tent and still be in great shape. Have fun!