The reality for many grassroots coaches
An assistant coach is genuinely useful — extra eyes, extra hands for setup, someone to help with a struggling player while the group continues. But many grassroots coaches run sessions solo, especially early on, and it's completely workable with a few adjustments.
Drills that work with one set of eyes
Activities where every player is doing the same thing at the same time (a rondo, a small-sided game, a whole-group technical activity) are far easier to run solo than activities involving multiple simultaneous stations — you can't watch three different things happening in different corners at once. When solo, fewer, simpler activities that everyone does together beat an ambitious multi-station plan you can't actually oversee.
Using players as helpers
Older or more confident players can help set up cones, demonstrate alongside you, or briefly lead a partner through a warm-up activity — not as a substitute for your coaching, but as a way of getting small tasks done while you focus on the group. Most kids enjoy being asked to help; it's not extra work for you to delegate it, it's often a genuine plus for them too.
Safety considerations when solo
Know where your group's boundaries are before starting (a session that can sprawl across a large area is harder to supervise alone), and have a simple plan for "what if a player needs individual attention" — e.g., a brief water break for everyone while you deal with one player, rather than the group continuing unsupervised while you're focused elsewhere.
Keeping it simple by necessity
A solo-coached session with 3 simple, well-run activities the whole group experiences together is better than an ambitious session with 6 activities that you can't actually deliver while watching everyone. "Simple but well run" beats "ambitious but chaotic" every time — and this is doubly true solo.
When to ask for help
If your group is large, includes players needing more individual attention, or you're finding solo sessions consistently stressful rather than just busy — asking your club for an assistant (even an occasional parent helper, suitably checked per your safeguarding policy) is a reasonable thing to raise. Plenty of clubs have parents willing to help who've just never been asked.